BEIRUT (AP) — Syrian rescue workers and a war monitor say talks to cede the largest opposition holdout in southwestern Syria to the government have failed, triggering an intense bombing campaign on the densely populated town that killed a dozen people and injured over a hundred.

Britain-based Syrian Observatory for Human Rights said an overnight 'frenzied' bombing campaign continued into Wednesday, with at least 350 missiles lobbed into Nawa and its surrounding areas. The Observatory said at least 12 were killed as rescuers struggled to get to the casualties.

Khaled Solh, head of the local Syrian civil defense known as White Helmets, said only one ambulance was able to access the town and civilians relied on their cars to bring out at least 150 injured.

Talks to hand over the town faltered Tuesday.