Two men arrested in connection with the failed 21 July London bombings are being questioned by police.
The men were arrested on Monday, following three raids at separate addresses in south London.
Officers with search warrants, supported by armed police, made the arrests after raiding one address in Clapham and two in Stockwell.
The men were held on suspicion of committing, preparing or instigating acts of terrorism.
Meanwhile Hussain Osman, who is accused of being behind the 21 July attack at Shepherd's Bush, has been charged under Italian anti-terrorism laws.
One of the sites of Monday's raids in Stockwell was still cordoned off with police tape on Tuesday.
SUSPECTED BOMBERS ARRESTED
1: Yassin Hassan Omar, 24, wanted over bomb attempt on a Tube near Warren Street, arrested in Birmingham
2: Ibrahim Muktar Said, 27, suspected of attempting to bomb a No 26 bus in Shoreditch, arrested in North Kensington, London
3: Ramzi Mohamed, wanted over failed attempt to bomb a Tube near Oval, arrested in North Kensington, London
4. Hussain Osman, 27 (also known as Hamdi Issac) wanted over the Shepherd's Bush attack, arrested in Rome
A man, who did not wish to be named, said the arrested man was his neighbour and of either Ethiopian or Somali origin.
"The police came at about 9pm," he said. "They said he was one of their suspects.
"I know him as a friend to talk to."
A local cafe owner described the man, in his 30s, as "very polite, and a very jokey guy".
In another part of Stockwell, a neighbour said a second arrested man was an Asian in his late 20s, who lived with his girlfriend and her two children.
Ahmet Tokmak, 41, said police arrived at the block of flats about 1730 BST on Monday and an hour later led out the man from the flat.
"My daughter started shouting that there were some people with guns outside.
"I went out because my six-year-old daughter was playing downstairs but the people started shouting at me to go inside.
"They were banging on the door downstairs and shouting and pushed the door down once it was opened. It was frightening."
In Italy, Antonietta Sonnessa said Hussain Osman, 27, was charged with association with the aim of international terrorism and with possessing false documents.
The move allows the authorities to continue holding Mr Osman - also known as Hamdi Issac - and is separate from Britain's attempt to extradite him.
Two of Mr Osman's brothers have also been arrested and questioned by police in Italy.
As the British police investigation into the failed bombings continues, six men and a woman remain in custody after being arrested during police raids in Brighton on Sunday morning.
They are being held under the Terrorism Act on suspicion of the commission, preparation or instigation of acts of terrorism, or harbouring fugitives.
Since the arrests on Friday of those suspected of carrying out the failed bombings, police are focusing on finding those who helped plan and finance the attacks, as well as those of 7 July.
Police have also been allowed extra time to question Yassin Hassan Omar, the man suspected to trying to blow up a train between Oxford Circus and Warren Street.
He can be questioned until Wednesday. He was arrested in Birmingham on 27 July.
Two other suspected bombers, Ibrahim Muktar Said, 27, and Ramzi Mohamed, remain in custody after being arrested during an armed raid in London on Friday.
Suspects can be held for a maximum of 14 days under the anti-terror laws before they must be charged or released.