More than 100 civilians have been killed in a new "massacre" in the Syrian city of Homs, a watchdog said Thursday.

More than 100 civilians have been killed in a new "massacre" in the Syrian city of Homs, a watchdog said Thursday, as Russia slammed the United States for blaming deadly blasts at a university campus on the Damascus government.

Witnesses said several members of the same family were among those killed, some in fires that raged through their homes and others stabbed or hacked to death. Among the dead were 32 members of the same clan.

Homs is the most strategic city in the country's largest province, lying on key trade routes near the borders with Lebanon and Iraq, and with its southwestern areas not far from Damascus.

The reported deaths were the latest to emerge from Syria, where twin blasts on Tuesday tore through an Aleppo campus while students were sitting exams.

At least 87 people were killed in one of the bloodiest attacks of the 22-month conflict committed by the armed opposition groups, in a city that has suffered some $2.5 billion in damage in six months of bitter conflict, according to Aleppo's governor.

The conflict has sent some 600,000 people fleeing the country, most of them to neighboring countries, according to the UN.