Gunmen opened fire in a bakery in eastern Baghdad today, killing eleven people, police said.

The attackers drove up in two cars and burst into the Happiness bakery, spraying bakery workers and customers with bullets.

The attack was being linked to a tribal conflict rather than to the insurgency. According to the AFP new agency, a police station opposite the bakery was untouched.

Yesterday 40 people died in rebel violence, which has risen ominously since the relative quiet during the security clampdown of the election on January 30.

The biggest attack occurred in Salman Pak, 12 miles (19 km) southeast of Baghdad, when insurgents attacked Iraqi policemen who came to look for weapons.

"According to our latest toll there were 10 police killed and 75 wounded," said a Salman Pak police officer. He added that 46 police vehicles were destroyed and that the fighting lasted several hours. Qassem Daoud, the National Security Adviser, said that 20 insurgents had been killed and 21 arrested.

"We have never seen such fighting," said the police officer in Salman Pak, a town which is fast becoming a hotspot in the clashes between the authorities and a loose alliance of hardline Wahabi Muslims, Saddam supporters and local crime lords.

US helicopters were sent to the scene and opened fired to dislodge the rebels. The town was sealed off on Friday by Iraqi and US troops but police said it was calm.

Iraqi officials announced yesterday they would seal the country’s borders for five days this month around a major Shia religious holiday. Last year during the holiday, about 180 people were killed in suicide attacks at Shia shrines.

Donald Rumsfeld, the US defence secretary, arrived in Mosul at dawn on a surprise visit to review Iraq security forces and to meet Iraqi and American leaders. Mr Rumsfeld's last surprise visit to Iraq was on Christmas Eve.

Times Recommends

• Michael Jackson: Not the final chapter
• Indian Army spends10m rupees on golf buggies
• Brüno toned down for 15 rating