Syria crisis: Houla 'massacre leaves 90 dead'
At least 90 people, including many children, have been killed in Syria's restive Homs province, opposition activists say, calling it a "massacre".
They said scores were wounded in the violence in Houla, as government forces shelled and attacked the town.
Shocking footage has emerged of the bodies of children killed as part of one the bloodiest attacks in one area since a nominal truce began in April.
The UN said its international monitors had visited the area.
France's Foreign Minister Laurent Fabius condemned the assault, and said he was making immediate arrangements for a Paris meeting of the Friends of Syria group, which includes Western and Arab nations, but not Russia or China, who have blocked previous attempts to introduce UN sanctions.
Fighting in Syria has continued despite the deployment of some 250 UN observers monitoring a cease-fire brokered by UN envoy Kofi Annan - a ceasefire which the BBC's Jim Muir in neighbouring Lebanon says is now "pretty fictional".
The UN says at least 10,000 have been killed since an uprising began in March 2011 against President Bashar al-Assad's rule.
Day of mourning
An activist in Houla told the Associated Press news agency that troops began the assault on Houla after an anti-regime demonstration following Muslim prayers on Friday.
The assault began with artillery shelling which killed 12, he said - but scores more were butchered when pro-regime thugs known as "shabiha" then stormed the area.
The UK-based Syrian Observatory for Human Rights said more than 90 people had died in the 24 hours since midday on Friday.
The opposition Syrian National Council (SNC) said more than 110 people died and urged the UN Security Council to act, AFP news agency reported.
Among the dead were more than 56 children, the SNC's Ausama Monajed told the BBC.
He said the regime was selecting vulnerable towns to "teach the entire country a lesson".
"It is beyond humanity what we have seen," he said.
Activists have called a day of mourning.
Horrific video footage has emerged of dozens of dead children, covered in blood, their arms and legs strewn over one another. It is unverified, but our correspondent says such images would be difficult to fake.
In one instance, six members of a family were killed when their house was shelled, the Observatory said.
At least 20 others were killed in violence elsewhere in Syria on Friday, according to activists.
International media cannot report freely in Syria and it is impossible to verify reports of violence.
Some of the 260 UN observers now in the country visited the Houla area after the assault, but there are no reports yet on what they found.
Earlier, a spokesman for UN-Arab League peace envoy Kofi Annan said he was planning to visit Damascus.
The spokesman declined to give a date, but diplomats in Geneva told AFP that the former UN secretary general would make the trip early next week.
'Evidence of shelling'
Meanwhile, in a letter to the Security Council, UN chief Ban Ki-moon said the Syrian opposition controlled "significant parts of some cities".
He said that "established terrorist groups" could have been behind some of the recent bomb blasts in Syria judging from the sophistication of the attacks.
He said the situation remained "extremely serious" and urged states not to arm either side in the conflict.
Earlier this month, a bombing in Damascus left 55 dead in an attack which the government blamed on al-Qaeda. The attack came amid mounting fears that the terrorist group was taking advantage of the conflict to gain a foothold.
Mr Ban said Syria "has not ceased the use of, or pulled back, their heavy weapons in many areas" - one of the requirements of Mr Annan's peace plan.
"On several occasions, UNSMIS has heard the sound, or seen evidence, of shelling in population centres," he said.
On Thursday, a UN-mandated panel said Syrian security forces were to blame for most abuses in the conflict, which has continued despite the presence of the UN observers.
Mr Annan's six-point peace agreement ordered a cessation of violence on 12 April. While casualties appeared to fall after the truce, the fighting quickly resumed to previous levels.