This article is more than 11 years old

This article is more than 11 years old

Thousands of protesters have blocked Parliament Square in central London, calling for a ceasefire in the Sri Lankan government's assault on the Tamil Tiger separatists.

They have surrounded a makeshift tent which houses hunger striker Parameswaran Subramaniyan, 28, who is in a critically weak condition after two weeks of protest. He says he will halt the action only if Britain helps secure a ceasefire in Sri Lanka.

"His condition is deteriorating day by day," Dr Arundkumar Velauthapillai said by his bedside. "He is not taking enough water but he is stable. He wants a ceasefire back home."

Parameswaran's spokeswoman, Raji Nesajah, said: "Britain has a moral responsibility to intervene. If he dies, it will be on Britain's hands."

At about 2pm today the Rev Nicholas Sagovsky, from nearby Westminster Abbey, persuaded Parameswaran to take a sip of drink during one of his daily visits to the hunger striker.

In a statement on Saturday night, the foreign secretary, David Miliband, said he was "gravely concerned" about the situation in Sri Lanka and the government was consulting "urgently" with the United Nations.

Miliband said the prime minister's special representative, Des Browne, was on his way to New York for talks on the Sri Lankan crisis with the UN. The foreign secretary also repeated his call for an immediate ceasefire.

Nesajah today criticised the police for trying to move Parameswaran's tent from Parliament Square over the weekend. Up to 10,000 people gathered around the square this morning, some carrying Tamil Tiger flags. Several hundred people sat on the street, blocking traffic.

They chanted: "Britain, Britain, save the Tamils" and "Gordon Brown open your eyes."

Police vans blocked the road from the square to Westminster Bridge, where the current demonstration started on 6 April.

The police want to keep the bridge open and avert a repeat of protesters throwing themselves into the river Thames.

The Houses of Parliament were partially closed to vehicles. Parliament Square was shut to traffic and vehicles were prevented from entering the main entrance to the House of Commons for cars.

MPs had to use the House of Lords entrance to drive into the parliamentary estate. Bridge Street, which leads to Westminster Bridge, and part of Whitehall were also closed to traffic.

A Metropolitan police spokesman said officers had been alerted to the protest this morning. He added that there had been no arrests.

He said: "We are aware of about 2,500 Tamil supporters gathering. We are policing it as a protest and will amend our operation as necessary."

Arun Sirthar, a 19-year-old student from Bournemouth, said the protesters might try to occupy the bridge later today. "I'm here for the Tamils that are dying right now."

On the first day of the demonstration two weeks ago, many of the protesters complained of police violence after officers forced them from Westminster Bridge to Parliament Square. Scuffles involving truncheon-wielding officers also broke out when officers tried to remove red Tamil flags.

Today the police asked protesters to move but took no action when they did not.At one point an inspector asked: "Is there anything I can do to stop you occupying the road?"

Another inspector was surrounded by chanting protesters when he went into the crowd to ask people to move.

The protesters represent a broad spectrum of the Tamil community in Britain, from small children to older people, many of whom were shielded from the April sun under umbrellas and pieces of card. The organisers handed out drinks and sandwiches.

Speaking from Parliament Square, the Labour MP Austin Mitchell, said: "It's chaos, isn't it? I'm sympathetic [to the protesters]. The Sri Lankan government seems to be going for the kill and that's the tragedy. There's a safe zone but it's not being respected."

He said the British government should help secure a ceasefire, but he added: "Militarily, there's nothing we can do."

Suren Surendiran, of the British Tamils Forum, said the demonstration was "spontaneous" and coincided with the reopening of parliament.

He said: "There have been texts going around as parliament opened today after the Easter recess and people have been encouraging their friends and families to gather.

"There is no point issuing statements. The British Tamil community do not want words any more, we want action.

"We want to see a British government take the matter to the UN security council to get a ceasefire implemented.

"This protest will make a difference because where else can people go? This is a peaceful demonstration. This is about brothers and fathers and sisters being killed. I know people who have lost 15 members of their family.

"These are people exercising their democratic right when people across the world are having their human rights trampled on."

Calls for a ceasefire have been rejected by the Sri Lankan government, which said a pause in the fighting would give Tamil Tiger rebels time to regroup. The remnants of the Tigers have retreated to a slice of land that has been declared a no-fire zone.

Miliband said: "Protests and demonstrations around the world have highlighted the tragic loss of life of innocent civilians in Sri Lanka. Further loss of life will only compound that tragedy.

"The Tamil community are a community we value and they make an important contribution to British society. They have seen friends and relatives perish and their loved ones are still at grave risk from the fighting.

"We have heard their voice and will keep listening. We are committed to do all we can to bring this terrible conflict to an end."

A hundred thousand protesters marched through central London earlier this month to draw attention to the Sri Lankan government's offensive against Tamil Tiger rebels and alleged human rights abuses.