At least 50 people have been killed and 700 injured in a series of explosions on the London Underground network and a bus in central London.
Eyewitnesses tell what they saw and heard at blast sites around the capital.
MICHAEL HENNING, LIVERPOOL STREET
We travelled out into the tunnel and not long after we set out all I saw was yellow light and what appeared to be silver lines in front of my eyes - which turned out to be the glass.
I was being twisted and thrown to the ground. I thought I wasn't going to get out of this - whatever it was - I just didn't know. I thought that was it when it went all so dark.
Then I touched my hand to my face and felt the blood and knew it wasn't all over yet.
I am an extremely lucky man, I am very lucky indeed, especially as I saw what happened in the next carriage.
The bomb must have been within 10 feet of me but that carriage took most of the blast and we were just showered in glass.
Our carriage was smoke-filled, there was lots of dust, there was lots of panic. We could hear the screams from the carriage where the bomb had gone off - they were trapped in twisted metal.
The doors wouldn't open... then we saw this orange jacket which turned out to be one of the drivers. We decided we were going to walk out down the middle of the train.
TANYA ALLEYWAY, LIVERPOOL STREET
Everybody was absolutely terrified. You could hear the screaming from the carriages in front, because that was where the explosion had happened, and there was lots of injured people there. Nobody knew what was going on.
The driver was trying to communicate with us, but the radio wasn't working.
People were trying to open the doors and the windows to let the smoke out and were rocking the train, which already felt like it had come off its rails.
So we were panicking that the train was going to get knocked over.
It was just general chaos. I thought I was going to die when I saw the flames. I thought we were going to get engulfed by the flames or get overwhelmed by the smoke.
I really didn't think we were going to get out. It hasn't quite sunk in, I think. It's the kind of thing where you see it on the news, but don't expect to be in it - and I was in it and it was horrible.
JOHN MAINGAY, TAVISTOCK SQUARE
I had just come out of my office to talk to colleagues about the news of an explosion in Liverpool Street.
Literally at that moment there was a huge "boom" outside.
I knew it was a bomb straight away. There was that smell of an explosion that accompanied it.
I saw lots of debris fly past the window, including one huge chunk.
It must have been the roof of the bus.
All non-medical staff, myself included, were evacuated out the back of the building, while doctors working in the building immediately went to the aid of the casualties.
Some were taken into the building and treated. Some of the building was also used as morgue.
I'm not sure how many died.
DAVID JONES, TAVISTOCK SQUARE
Suddenly there was this thud, people on the bus said there's been an explosion behind us and people rushed to the front.
I said to people not to panic, keep calm. People evacuated our bus.
There was not a lot of fire but there was the smell of an explosion and at that point people wanted to walk away from what they had seen.
There was no glass falling... there was a thud and the roof had come off.
I suppose, to be honest, my first thought was G8, Olympics, somebody does not want London to celebrate.
UNNAMED WITNESS, TAVISTOCK SQUARE
I was walking along. There was a crowd of people around the bus.
The next thing I knew I was on the floor. There was shed loads of glass raining down.
Someone fell on me and someone fell on him. For a moment I thought I was going to be trampled.
I picked myself up and everyone was running. There was glass everywhere.
We ran into a building and a security guard was saying `get in, get in'. Then the security guard said `get out'... which was a bit scary.
I saw the bus ripped out at the back ... it couldn't have been anything else [but a terrorist attack].
BELINDA SEABROOK, RUSSELL SQUARE
I was on the bus in front and heard an incredible bang, I turned round and half the double-decker bus was in the air.
It was a massive explosion and there were papers and half a bus flying through the air.
There must be a lot of people dead as all the buses were packed, they had been turning people away from the tube stops.
We were about 20 metres away, that was all.
GERALDINE FOURMON, TAVISTOCK SQUARE
There was a big bang. After the smoke went away I realised there was a double decker bus exploded. People were running towards me screaming and crying.
I saw at least five people jump from the top deck of the bus. Half of it was blown away. They were jumping onto the street to escape.
It was such a big explosion and the bus was packed because the tube was closed. People were covered with dust and debris. I didn't see any blood.
ANDY ABERNETHY, LONDON
It was a train on the Piccadilly line between King's Cross and Russell Square and literally it was just a very loud bang. The train derailed.
There was smoke everywhere. There was no fire but the smoke was quite oppressive.
There were a lot of serious injuries down there as well. A lot of serious head injuries.
A guy by me thought he was going to die, I'm hoping he got out OK.
JACQUI HEAD, KING'S CROSS
Suddenly there was a massive bang, the train jolted. There was immediately smoke everywhere and it was hot and everybody panicked.
People started screaming and crying.
It was very scary while we were stuck on the train. Very silent and we were thinking we were not going to get out.
People thought they were just going to suffocate.
TAS FRANGOULLIDES, KING'S CROSS
The train didn't get very far out of the station when there was an explosion.
Loads of glass showered down over everyone, the glass in the doors in between all the carriages shattered.
There was a lot of smoke and a lot of dust, there were some areas of panic, I could hear screams. People were trying to work out what happened.
A lot of people were covered in blood.
I started walking towards Russell Square then I saw the bus. Police were running from the scene and waving people away.
I had to walk to work because I had to try and do something normal, it was all so chaotic.
It wasn't till I got to work that I realised I had a cut on my head and my clothes were covered in dust.
FIONA TRUEMAN, KING'S CROSS
It was about three minutes after we left King's Cross, when there was a
massive bang and there was smoke and glass everywhere - I was standing near a
window, and I've still got some in my hair.
The lights went out, and with the smoke, we couldn't breathe, and we sort of
cushioned each other during the impact because the compartment was so full.
It felt like a dream, it was surreal.
It was just horrendous, it was like a disaster movie, you can't imagine
being somewhere like that, you just want to get out.
I kept closing my eyes and thinking of outside.
It was frightening because all the lights had gone out and we didn't hear
anything from the driver, so we wondered how he was.
Overall I feel lucky, and my thoughts go out to the families of anyone who
There was a loud bang and the train ground to a halt. People started panicking, screaming and crying as smoke came into the carriage.
A man told everyone to be calm and we were led to safety along the track.
Everyone was terrified when it happened.
When they led us to safety, I went past the carriage where I think the explosion was. It was the second one from the front.
The metal was all blown outwards and there were people inside being helped by paramedics.
One guy was being tended outside on the track. His clothes were torn off and he seemed pretty badly burned.
ANA CASTRO, LIVERPOOL STREET
People were screaming and shouting and saying things like I'm dying, I'm dying, please help me.
I saw people just standing there in their underwear as if their clothes had been ripped off [by the explosion].
I think I saw somebody who was dead it was just indescribable.
LISA CURTIS, NEAR LIVERPOOL STREET
People were evacuated immediately. I overheard one lady saying to a police officer that it looked like someone had left what looked like a brown jumper on the platform and it exploded.
Smoke filled the platform and people were evacuated.
SARAH REID, NEAR LIVERPOOL STREET
I was on the train and there was a fire outside the carriage
window and then there was a sudden jolt which shook us forward.
The explosion was behind me.
Some people took charge. We went out of the back of the carriage.
There was really hard banging from the carriage next door to us.
That was where it happened.
A carriage was split in two, all jagged, and without a roof, just open.
I saw bodies, I think.
SCOTT WENBOURNE, ALDGATE
I saw three bodies on the track. I couldn't look, it was so horrific. I think one was moving but I'm not too sure.
There were also, I think, some bodies in the carriage, some were moving but I couldn't really look. No-one was attending to them.
We walked to the platform, which took about half an hour as there were so many of us, after all it was rush hour.
There were police at the platform and some of the injured were tended to.
JACK LINTON, 14, ALDGATE
There was a massive explosion, smoke and flames. My carriage must have been two away from where it was.
Everybody got on the floor. Then eventually the smoke cleared and we managed to open the central doors down the train to go to the back of it before they walked us along the track past the train to the station.
The middle of the train was blown out and there were people on the track.
I've got glass in my hair and my pockets and my ear hurts.
DELME JENKINS, KING'S CROSS
I was coming into work on the bus and I saw a woman who looked as if she'd been crying with mascara running down her face which I thought was a bit strange.
Then I saw people wiping black dust off their faces and I knew something strange had happened.
It is shocking, there is a very strange atmosphere around. There is no traffic, people look lost.
SIMON CORVETT, EDGWARE ROAD
All of sudden there was this massive huge bang. It was absolutely
deafening and all the windows shattered.
The glass did not actually fall out of the windows, it just cracked.
The train came to a grinding halt, everyone fell off their seats.
There were just loads of people screaming and the carriages filled with
You couldn't really breathe and you couldn't see what was happening. The
driver came on the tannoy and said `We have got a problem, don't panic'.
You could see the carriage opposite was completely gutted.
There were some people in real trouble.