BEIRUT — A Syrian government airstrike hit a house in a rebellious suburb of Damascus early Monday, killing at least 13 people, including eight children, and trapping others under the rubble, activists said.

President Bashar Assad's forces have intensified their ongoing campaign against the towns and villages around Damascus, underlining the regime's resolve to crush the rebels a week after the Syrian leader defiantly rejected any talks with the armed opposition.

Activists said at least 45 people were killing in the government barrage on Sunday, and they described the bombardment over the past 24 hours as some of the heaviest in the Damascus region since the government launched an offensive in November to dislodge rebels from the capital's outskirts.