Syria Crisis: Homs fighting leaves 50 dead.
25 May 2012 Last updated at 23:08 GMT
Syria crisis: Homs fighting 'leaves 50 dead'
Protesters came out onto the streets after Friday prayers in cities across Syria
Continue reading the main story Syria Crisis
At least 50 people, including 13 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.
If the toll is right, it would be one of the bloodiest attacks in one area since a nominal truce began in April.
Meanwhile, UN chief Ban Ki-moon said the opposition controlled "significant parts of some cities".
In a letter to the Security Council, Mr Ban said the situation remained "extremely serious" and urged states not to arm either side in the conflict.
At least 20 others were killed in violence elsewhere in Syria on Friday, according to activists, after tens of thousands of protesters took to the streets after prayers.
'Mangled bodies' In Houla, Syrian forces used tanks, mortars and heavy machine guns, according to both the Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees activist groups.
The BBC's Jim Muir in Beirut says unverifiable video posted on the internet by activists showed the bloodstained and mangled bodies of many children huddled on a floor in the dark, with the commentator shouting that there were too many to count.
Activists said several whole families were slaughtered by security forces on the edge of town. Some died in heavy shelling, while others who were caught were summarily executed, our correspondent says.
In one instance, six members of a family were killed when their house was shelled, the Observatory said.
International media cannot report freely in Syria and it is impossible to verify reports of violence.
The BBC's correspondent Paul Wood and cameraman Fred Scott report from the rebel stronghold of Rastan
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.