The US military said it was not responsible.

Residents of Nasaf, a town just outside Ramadi, west of Baghdad, said a roadside bomb exploded next to a US armoured patrol as it passed near the Ibn al-Jawzi mosque shortly after prayers on Friday.

Following the explosion, US troops opened fire towards those emerging from the mosque, the residents said.

Pools of blood lay on the steps outside the mosque and bullet holes marked its walls.

Dr Munem Aftan, the director of Ramadi General Hospital, said seven adults and eight children were killed and 17 wounded.

But the US military said its troops had not been involved in any firing in the area.

"US forces were not involved in any shooting incident in eastern Ramadi or anywhere near a mosque," Captain Jeffrey Pool, a spokesman for the Marines in Ramadi, said in an e-mail reply to written questions.

"US forces were certainly not involved in any indiscriminate fire incident," he said.

He did not say whether an attack on a US patrol had occurred or whether any US troops were wounded.

The death toll was initially reported as two dead, but doctors said it had risen sharply overnight, with several of the severely wounded succumbing to their injuries.

Iraqi civilians frequently complain that US troops open fire indiscriminately after they are attacked.

The US military says it does everything possible to avoid civilian casualties and is careful to respond to attacks in a measured fashion.

Human rights groups have documented scores of cases in which civilians have been shot and killed after approaching US military roadblocks too quickly, or not following instructions to keep away from US military convoys as they pass.

Roadside bombs - large or small amounts of explosives buried in the side of the road and remotely detonated - are the biggest killer of US troops in Iraq.

A US general said on Friday that roadside bomb attacks on US supply convoys in Iraq had doubled in the past year, although the number of casualties had declined because of increased use of armoured vehicles.