Baghdad: Iraqi and US troops launched an operation in northern Iraq on Saturday to try to drive out Al Qaida fighters who regrouped there, the Iraqi military said.

Lt Gen Riyadh Jalal Tawfiq, commander of Iraqi armed forces in Nineveh province, said the operation would particularly target Al Qaida fighters in the city of Mosul, regarded as the group's last urban stronghold in Iraq.

Tawfiq said a vehicle curfew had been imposed throughout the province, whose capital is Mosul.

"I declare the beginning of the military operation today to clean the province of Al Qaida remnants," Tawfiq told reporters. "I call on all the clerics and the heads of tribes to support the security forces in our effort to kick Al Qaida out."

The US military had no comment. Mosul residents said they saw US fighter planes flying over the city.

Tawfiq said large numbers of Iraqi forces had been sent to Nineveh for the operation, although he declined to give details.

In January, Prime Minister Nouri Al Maliki announced plans to drive Al Qaida out of Mosul, Iraq's third-largest city.

US military officials said at the time it would take months to clear the ethnically and religiously mixed city.

US officials blame Al Qaida in Iraq for most big bombings in the country, including an attack on a Shiite shrine in Samarra in February 2006 that set off a wave of sectarian killings that nearly tipped Iraq into all-out civil war.

A build-up of US troops last year and support from Sunni Arab tribes that turned against Al Qaida allowed the military to conduct a series of offensives that largely pushed the fighters out of Baghdad and the western province of Anbar.

Many regrouped in northern provinces, such as Nineveh.

However, US commanders say Al Qaida in Iraq, although weakened, can still carry out large-scale attacks.

Al Qaida in Iraq shares the name and ideology of Osama Bin Laden's network, which was blamed for the September 11, 2001 attacks in the United States.

Structural and operational ties between the two are unclear but the US military says Al Qaida in Iraq is largely foreign-led. Its foot soldiers are mainly Iraqis.