Britain, France and the US join co-ordinated international action after massacre of more than 100 people in Houla

Governments around the world expelled Syrian ambassadors and diplomats on Tuesday in a co-ordinated protest at the massacre of more than 100 people, including scores of children, in Houla last weekend.

Britain, France, Germany, the United States and Canada were among those taking part in the global diplomatic action, which came as a UN report said many of those killed were shot at close range.

Kofi Annan, representing the UN and the Arab League, met the Syrian president, Bashar al-Assad, in Damascus "to convey the grave concern of the international community about the violence in Syria" and the prospects for the implementation of his apparently failing six-point plan.

Australia also said it was expelling the Syrian ambassador. Germany announced it was expelling the Syrian envoy, and Spain, Italy and the Netherlands are due to do the same.

The US state department said that the Syrian charge d'affaires, Zuheir Jabbour, the most senior Syrian diplomat in Washington, was being given three days to leave the country.

"We hold the Syrian government responsible for this slaughter of innocent lives," said the state department spokeswoman, Victoria Nuland. "This massacre is the most unambiguous indictment to date of the Syrian government's flagrant violations of its UN security council obligations."

Syria withdrew its ambassador from Washington in December after the US closed its embassy in Damascus, along with Britain and France, over the violent crackdown against opponents of the Assad regime.

The UN's human rights office said on Tuesday that most of the 108 victims of the Houla massacre week were shot at close range, some of them women, children and entire families gunned down in their homes. Fewer than 20 people cut down by regime shelling.

Syria has flatly denied responsibility for the atrocity, calling it a "terrorist massacre".

France's president, François Hollande, was the first European leader to announce the expulsion of the ambassador, describing it as "not a unilateral decision but in consultation with our partners".

William Hague, the British foreign secretary, said the expulsions aimed to tell Assad and his ruling elite that time was running out for them to comply with the peace plan. "The world, the international community, is appalled by the violence that has continued, by the behaviour of the regime, by the murder of so many innocent people, including in the terrible massacre at Houla," Hague said.

It was not immediately clear why other members of the 27-strong EU had not joined in.

The announcement in Washington came later than in other capitals because diplomatic protocol required that the US state department first to call in Jabbour before making the move public.

Britain withdrew its ambassador and in effect closed its embassy in Damascus on security grounds earlier this year. That meant there was little to lose by taking this punitive step. But its effect will be largely symbolic, as Syria's ambassador, Sami Khiyami, left London some months ago. The charge d'affaires, Ghassan Dalla, was given the news when he was called into the Foreign Office. Two other Syrian diplomats have also been told to leave the UK.

Annan met Assad "to convey the grave concern of the international community about the violence in Syria, including in particular the recent events in Houla," reported his spokesman, Ahmed Fawzi. "He conveyed in frank terms his view to President Assad that the six-point plan cannot succeed without bold steps to stop the violence and release detainees, and stressed the importance of full implementation of the plan." Annan is to give a press conference later.

Survivors and witnesses cited by the UN blamed the house-to-house killings on pro-government thugs known as shabiha. "What is very clear is this was an absolutely abominable event that took place in Houla, and at least a substantial part of it was summary executions of civilians, women and children," said Rupert Colville, spokesman for the UN high commissioner for Human Rights. "At this point, it looks like entire families were shot in their houses."