The New York Times reports: A large number of Syrian civilians died in a poor neighborhood of Hama after their houses crashed down on them, but the government and the opposition offered widely different accounts on Thursday of the cause of the episode.

The opposition activists called it a massacre, saying intensive government shelling collapsed a row of cinder-block shanties, killing around 70 people. State media, however, said 16 people died when a bomb-making operation by government opponents went awry, with a series of blasts leveling the houses in the Mashaa al-Tayar neighborhood.

The Syrian Observatory for Human Rights, based in London, had a similar lower toll, but said the cause of the deaths was as yet undetermined.

The episode was certain to deepen the skepticism that a shaky cease-fire negotiated by Kofi Annan, the former United Nations secretary general, would hold.

A new pattern has also developed in recent days of the government rushing to blame the opposition, which it uniformly labels “terrorists,” for deaths in episodes of violence. On Tuesday, Mohamed Khadra, a volunteer for the Syrian Arab Red Crescent, was killed in a hail of gunfire that hit an ambulance ferrying the wounded from the Damascus suburb of Douma. The opposition has accused government forces of repeatedly preventing the evacuation of wounded from neighborhoods that staged antigovernment protests, while the state-run media blamed an “armed terrorist group” for the attack.

In Istanbul on Thursday, the Syrian National Council, the main opposition group in exile, issued a statement describing the deaths in embattled Hama as a blatant violation of the cease-fire. It called on the United Nations Security Council to meet to do something more to protect Syrian civilians. The government of President Bashar al-Assad had committed a series of “crimes” against Hama residents, including heavy shelling, summary executions, raids and arrests, it said.