In what could be the bloodiest event of the Syrian uprising so far, a government offensive in the western Hama region resulted in the deaths of hundreds of people, most of whom were civilians, according to opposition activists.

More than 220 people fell today in [the Sunni village of] Taramseh. They died from bombardment by tanks and helicopters, artillery shelling and summary executions, said one local opposition group in a statement, according to Reuters.

Fleeing activists said that government forces swept into the village after rebel fighters had withdrawn.

Every family in the town seems to have members killed. We have names of men, women and children from countless families, said an activist named Fadi Sameh, whose family is from Taramseh.

The popular uprising against Assad began in March of last year. Loosely organized opposition fighters have struggled against Assad's formidable forces for the past 16 months. The conflict has claimed at least 14,000 lives so far, and violence is ongoing.

Kofi Annan, the Arab League's and the United Nations' joint special envoy for Syria, strongly condemned Thursday's violence.

I am shocked and appalled by news coming out of the village... of intense fighting, significant casualties, and the confirmed use of heavy weaponry such as artillery, tanks and helicopters, said Annan, according to the BBC.

This is in violation of the government's undertaking to cease the use of heavy weapons in population centers and its commitment to the six-point plan.

Annan's peace plan, agreed to by the Syrian regime and opposition representatives in March, included a cease-fire that was immediately broken. On Saturday, after three months of steadily increasing violence, Annan admitted his peace plan had failed.

Now, Annan says that UN observers are ready to visit Taramseh to investigate the incident.