UN Chief says Syria 'in contravention' of peace plan

The Syrian government is "in contravention" of an internationally agreed peace plan by keeping troops and heavy weapons in cities, Ban Ki-moon, UN secretary-general, has said.

He also said he was "gravely alarmed" by reports of shelling of populated areas in Syria, in a statement released after a deadly explosion on Thursday in the flashpoint city of Hama.

Activists blamed the government for the blast and put the death toll at 69, including 16 children. Syrian state media said 16 people were killed when a bomb that "terrorists" were building exploded prematurely inside a house .

Ban demanded that Damascus comply with the peace plan without delay.

The violence comes despite a UN-brokered ceasefire - part of the six-point peace plan proposed by the joint UN-Arab League envoy Kofi Annan.

The plan calls on Damascus to withdraw troops and heavy weapons from cities.

In a separate development, the Arab League said it would urge the UN Security Council to act "immediately" to protect Syrian civilians.

In a statement, the league said the issue would be raised at next week's council meeting.

France earlier said the council should consider the use of force in Syria if the peace plan fails to stop the violence.

Meanwhile, a video has emerged which purportedly shows a man being buried alive by security forces, allegedly for sending material to TV stations.

Its authenticity could not be confirmed.

The unnamed man, who is said to be a media activist, is seen pleading for his life as earth is shovelled over his head. He then goes silent.

What appear to be members of the security forces are then heard cursing him for receiving money for sending material to Arabic satellite TV stations.

The video was said to have been leaked by sympathisers.

The UN says about 9,000 people have died since pro-democracy protests began in March 2011. In February, the Syrian government put the death toll at 3,838 - 2,493 civilians and 1,345 security forces personnel.