People in and around Tibet have been sending the BBC their accounts of the most recent tension and violence.
A Tibetan man in Aba, Sichuan province described the atmosphere in the area on Tuesday.
In our area, we believe the number of deaths has reached 17. I know one of the dead, a girl. I know who her father and mother are.
She went to Tibetan Upper Middle School here.
Earlier today, the whole town was teeming with police and soldiers. All the shops have been closed. There are no arrests that I know of.
I also don't think anything is happening at the monastery here.
But there is tension everywhere. People are anticipating that something big is going to happen. I don't know what but we are anxious.
A Chinese businessman who wishes to remain anonymous described the scene in Lhasa on Monday.
On Monday we were allowed to go on the street along Beijing East Road and even Jiangsu Road.
Barkhor Square is still full of trucks at the moment. The army let people go in and out only if they have the temporary residential permits.
The road checks are very frequent and we were requested to show our identity cards or passports at many places. You can tell from their gestures that the army might not be well-trained in checking passports.
We walked down the Beijing East Road and saw for the first time the destruction of the riot. It's simply a mess - many passers-by tried to take pictures with their mobile phones but were politely requested to delete the photos, if found by the army.
Most of the Chinese and Hui Muslim places were targeted, many Hui Muslim beef shops were burnt, also stationery shops, banks, a wholesale market at Tsomtsikhang (one of the most important Tibetan markets, where many shops are owned by Chinese and Hui Muslims).
The foreign-owned Dunya was okay but another foreign-owned French restaurant had been smashed with stones.
A Tibetan lady who run a small Indian-imported goods shop said it was really bad on the day of riots - some people went into her shop, not to destroy her shop but just to rob it. She told the rioters that she wasn't going to survive if she couldn't run this shop, then the Tibetan rioters left the place.
She said she was so scared because many people were carrying long knives.
It was good to see many friends. Most of my friends' places were okay except one lady from Beijing. Her souvenir shop in Mentsikhang Road (Tibetan Hospital Road) was looted. She is still in Beijing now and is worrying about the shop.
Many shops put white scarves (called Kata in Tibetan) outside to signify a respect for things Tibetan and many shops survived perhaps because of the power of Kata.
We even went into two restaurants to have some real food instead of instant noodles. That was good.
We came back to the hostel at around 9pm but the road was blocked again, the army said they had a special order to block the road every day after 7pm.
At first they didn't want to let us in, but after seeing our identity cards and consulting their patrol leader, we were finally allowed back.
Swiss tourist Claude Balsiger told the BBC's Charles Haviland in Nepal about the violence he witnessed in Lhasa and the atmosphere in the city as he left. These are a selection of his comments.
We were in the centre of Lhasa when the first demonstrations happened on Monday 10 March. We saw the first civilian persons getting arrested on Tuesday on Barkhor Square right downtown.
There was lots of tension and heaps of soldiers, police, undercover police, secret police everywhere. They followed us back to the hotels. That was all before the riots on Friday.
On Friday I was having tea in a cafe above Barkhor Square. At about 1230 I walked down across the square and popped out on Beijing East Road and there were three army trucks which dropped off about 30-40 soldiers.
The soldiers were already trying to shelter in a small alleyway because there was a crowd of about 500 people throwing stones. That took about four or five minutes until they had to retreat and they ran for their lives down the alleyway.
I was personally there when they [the crowd] started beating up an old Chinese man on a bicycle. They hit his head really hard with stones. And some old Tibetan people went into the crowd and made them stop.
But after that it just went insane. It was mainly young people but the young people were in the action and the older ones were just supporting them with screaming. They were making a wolf sound, howling like wolves.
The Tibetans I talked to were talking of over 100 Tibetans killed and 1,000 arrested. The atmosphere in the last couple of days has been really, really tense. Yesterday we were allowed out onto the streets for the first time. There were military checkpoints every 10-15m. We had to keep our passports to show everyone.
I was in front of Beijing East Road. Across the street there was a Chinese couple taking pictures of soldiers. Every soldier had the bayonet on his rifle and one of the soldiers saw that, aimed his weapon at them, loaded the weapon and ran across the street to them. He brought them to his office to erase those pictures.
The police and military were out in force in Lhasa after the protests
There were a few police, paramilitary, heaps of army. On Beijing East Road there may have been 20 tanks with soldiers on them. The soldiers were really young and nervous.
From their faces they looked about 16 or 17 years old, with bayonets and always with fingers on the trigger. That's what made us really nervous.
Everyone is really, really scared. Even during the riots when there was no police around, no one would really talk to you. Everyone was trying to keep quiet because they are all really afraid. We wanted to leave because everyone was really afraid of a crackdown on Monday night after the end of the ultimatum.