A massive explosion in the Syrian city of Hama has killed 70 people, according to opposition forces.

But while rebels claim the blasts were caused by intense shelling, state media organization SANA said armed terrorist groups had accidentally detonated a bomb that leveled nearby buildings.

The agency also denied that so many had been killed, putting the figure at around 16.

The latest violence comes a day after French Foreign Minister Alain Juppe joined the U.S. in proposing possible military action against Syria's President Bashar al-Assad if his security forces continue to ignore a United Nations-mandated peace plan.

The call brings France in line with U.S. Secretary of State Hillary Clinton who, during a Friends of Syria meeting of world powers in Paris last week, also suggested more forceful action in Syria.

We think this mediation should be given a chance, on the condition that the deployment of the observer mission happens quickly, Juppe said after a meeting with Syrian dissidents at his ministry, according to the Associated Press.

Elsewhere, a video has emerged allegedly showing a man being buried alive after he was caught filming security forces.

The unnamed man is seen buried with just his blindfolded head showing, as he is surrounded by what appear to be government troops and their commander.

He is then heard pleading for his life as soldiers shovel dirt on top of him.

According to activists nearly 100 people have been killed in recent fighting between Assad's troops and rebel forces, with reports of widespread violence pouring in from around Syria.

The news comes after UN peace envoy Kofi Annan told the Security Council on Tuesday the situation in Syria was bleak, amid reports that Assad's forces had entered the city of Hama on Monday after UN observers left, reportedly killing more than 30 people.

Annan's spokesman Ahmad Fawzi told journalists: They are entering areas where there has been conflict like Homs and Hama and when they go [there] the guns are silent, according to Reuters.

When they leave, the exchanges start again.

We have credible reports that ... these people who approach the observers may be approached by security forces or Syrian army and harassed or arrested or even worse, perhaps killed.