BEIRUT - The death toll from Syria's crackdown on an 8-month-old revolt has exceeded 4,000 people and the country's leaders should be prosecuted for crimes against humanity, the UN's top human rights official said Thursday.

The scathing criticism from the UN High Commissioner for Human Rights Navi Pillay comes as the pressure piles on Syrian President Bashar Assad from home and abroad. But Assad has shown no signs of softening, raising fears the country could be sliding toward civil war.

"We are placing the figure at 4,000 but really the information coming to us is that it's much more than that," Pillay told reporters in Geneva.

Also Thursday, the European Union imposed fresh sanctions on Damascus, and the Syrian opposition called a general strike inside the country, ramping up efforts to persuade the country's business elite to abandon their long-standing ties to the regime.

The recent spate of economic sanctions from the EU, the Arab League and Turkey are punishing Syria's ailing economy, a dangerous development for the government in Damascus. Syrian business leaders have long traded political freedoms for economic privileges in the country, where the prosperous merchant classes are key to propping up the regime.

But the sanctions, coupled with increasing calls for strikes, could sap their resolve.

The new EU sanctions target 12 people and 11 companies, and add to a long list of those previously sanctioned by the EU. The full list of names of those targeted will not be known until they are published in the official journal of the EU on Friday.

The 27-member bloc also imposed some sanctions on Syria's ally Iran in the wake of an attack this week by a mob on the British Embassy in Tehran, the Iranian capital.

British Foreign Secretary William Hague accused Iran of supporting Assad's crackdown, saying "there is a link between what is happening in Iran and what is happening in Syria."

The sanctions came as Syrian troops stormed a village in the central province of Hama, killing at least six people -- the latest in what has become daily violence and bloodshed in the country.

It was difficult to gauge how widely Syrians were abiding by Thursday's strike, which activists announced on an opposition Facebook page. The regime has sealed the country off from foreign journalists and prevented independent reporting.

Residents in Syria's two economic powerhouses -- the capital, Damascus, and the northern city of Aleppo -- reported business as usual Thursday.

But in the flashpoint city of Homs, a resident told The Associated Press that most of the shops were closed, except for those selling food. Homs has been one of Syria's most volatile cities, with increasing clashes between troops and army defectors.

"Few people are in the streets and only about 20 per cent of students went to schools and universities," said one resident, who asked that his name not be made public for fear of government reprisals.

A video posted online by activists showed mostly closed shops in the Damascus suburb of Zabadani, which also has seen large anti-regime protests.

Despite the recent diplomatic squeeze and Thursday's strike, the government has shown little sign of easing its crackdown.

The Local Coordination Committees activist group said security forces swept through the village of Traimseh in the central province of Hama. The group said six people were killed, without giving further details.

The British-based Syrian Observatory for Human Rights also said six people were killed and nine wounded in Traimseh. It added that the operation was continuing in the village.

Also Thursday, the government took local journalists on a trip to the village of Kfarbo in Hama province, where they spoke to the family of a 9-year-old boy who was shot dead in Homs three days ago while he was buying cookies from a shop.

"He was holding a biscuit in his hand not a pistol," the child's mother, Georgina Mtanious al-Jammal, told reporters. "They have burned my heart."

She blamed "armed terrorists" for killing her son.

The shooting is particularly resonant in Syria because the boy, Sari Saoud, was from a Christian family. Christians and other religious minorities in Syria generally support the regime because they feel it offers them important protections.

Syria is overwhelmingly Sunni Muslim, and many minorities fear they will be marginalized if a Sunni regime takes over. Assad and the ruling elite are from the tiny Alawite sect.