The Syrian charge d'affairs is to be summoned to the Foreign Office to hear Britain's condemnation of the "stomach-churning" massacre of civilians, including dozens of children.

The diplomatic dressing down comes amid international outrage at the images from Houla after it was shelled by President Bashar Assad's regime forces.

More than 90 people were killed, including at least 32 children under 10, according to United Nations observers.

Foreign Secretary William Hague is calling for an urgent meeting of the UN Security Council to co-ordinate a "strong" international response. Foreign Office minister Alistair Burt said the council would need "all the options on the table".

After what was one of the Syrian regime's deadliest attacks in the country's 14-month-old uprising, gruesome video emerged showing rows of dead Syrian children lying in a mosque with gaping head wounds.

Deputy Prime Minister Nick Clegg told BBC1's Andrew Marr Show: "The scenes of savagery that we have seen on our television screens are revolting, stomach-churning."

Mr Burt said the Foreign Secretary would be meeting the Russian foreign minister in Moscow. Russia and China have been the principle opponents of stronger action against the Syrian regime by the UN.

"There should be an urgent meeting of the Security Council and they will have to have all the options on the table that they need in order to show that the international community cannot be thwarted," Mr Burt told Sky News.

The Syrian charge d'affairs will on Monday meet the Foreign Office's political director, Sir Geoffrey Adams, who will inform him in person of Britain's condemnation of the regime's actions.

In a statement on Saturday, Mr Hague said: "Our urgent priority is to establish a full account of this appalling crime and to move swiftly to ensure that those responsible are identified and held to account."