The US military in Iraq has said 10,000 US and Iraqi troops are taking part in an operation against al-Qaeda networks north of the Iraqi capital, Baghdad.
The US military has said 10,000 US and Iraqi troops are taking part in a major operation against militants linked to al-Qaeda north of the capital, Baghdad.
The troops were said to be moving in and around the city of Baquba in Diyala province, which is considered to be an al-Qaeda stronghold.
The offensive started early on Tuesday with a ground and air assault to secure the city of Baquba in Diyala Province, a centre of the Sunni Arab insurgency.
The US military said 22 militants had been killed early in the offensive, called Operation Arrowhead Ripper.
The US says 22 militants have been killed, but local officials say there have also been civilian deaths.
Meanwhile police say at least 40 people have died in a car bomb in Baghdad.
The massive explosion near a Shia mosque, which wounded at least 70 others, rocked the centre of the capital and sent large clouds of black smoke into the air.
The bombing came only days after suspected Sunni militants attacked the al-Askari shrine in Samarra, one of the most revered sites in Shia Islam.
Night-time assault
In Diyala, Operation Arrowhead Ripper began overnight with troops being brought in by helicopter.
The end state is to destroy the al-Qaeda influences in this province and eliminate their threat against the people Brig-Gen Mick BednarekUS military spokesman
Tanks and armoured vehicles were also used on the ground, with Apache helicopter gunships providing air cover.
"Task Force Lightning commenced Operation Arrowhead Ripper today in a large-scale effort to eliminate al-Qaeda in Iraq terrorists operating in Baquba and its surrounding areas," the US military said.
"The end state is to destroy the al-Qaeda influences in this province and eliminate their threat against the people," said US commander Brig-Gen Mick Bednarek.
The operation's chances of success have been improved by information provided by former insurgents, the military added.
"Over the past several weeks, we've seen that a number of the former insurgent groups, Sunni groups, are actually growing very tired of the al-Qaeda influence in the province - tired to the point where they're giving coalition and Iraqi security forces information that has been very helpful," US Sgt Thomas Clementson told the BBC World Service's World Today programme.
'Clear, hold and build'
Diyala province has seen some of the worst violence in Iraq this year.
Diyala province has seen some of the worst violence in Iraq this year.
Insurgent groups have moved there in the face of the US troop build-up in Baghdad.
The latest operation's strategy is the same as in Baghdad - clear, hold and build, according to the BBC's Andrew North in the capital.
The latest operation's strategy is the same as in Baghdad - clear, hold and build, according to the BBC's Andrew North in Baghdad.
US troops do the initial clearing and Iraqi forces hold areas afterwards, followed by rebuilding efforts to win people over, he says.
US troops do the initial clearing and Iraqi forces hold areas afterwards, followed by rebuilding efforts to win people over, he says.
But the approach has met with mixed success in Baghdad so far and, as has happened so often, the insurgents respond by simply moving elsewhere, our correspondent adds.
But the approach has met with mixed success in Baghdad so far and, as has happened so often, the insurgents respond by simply moving elsewhere, our correspondent adds.
Night-time assault
The US military is due to report on the success of the build-up in September.
The operation, which is continuing, began overnight with troops being brought in by helicopter.
Tanks and armoured vehicles have also been used on the ground, with Apache helicopter gunships providing air cover.
"Task Force Lightning commenced Operation Arrowhead Ripper today in a large-scale effort to eliminate al-Qaeda in Iraq terrorists operating in Baquba and its surrounding areas," the military said.
"The end state is to destroy the al-Qaeda influences in this province and eliminate their threat against the people," said US commander Brig Gen Mick Bednarek.
The operation's chances of success have been improved by information provided by former insurgents, the military said.
"Over the past several weeks, we've seen that a number of the former insurgent groups, Sunni groups, are actually growing very tired of the al-Qaeda influence in the province - tired to the point where they're giving coalition and Iraqi security forces information that has been very helpful," US Serg Thomas Clementson told the BBC World Service's World Today programme.
The US military is due to report on the success of its troop build-up, which is aimed at bringing Iraq under control, in September.
More than 20,000 US reinforcements are being deployed as part of the surge.
In July, funding measures go before the US Congress and in September, political and military assessments of the surge and the overall situation in Iraq are due.
In July, funding measures go before the US Congress and in September, political and military assessments of the surge and the overall situation in Iraq are due.
Are you in Iraq? Have you seen any troop movements? If you have any information you would like to share with the BBC you can do so using the form below:
Are you in Iraq? Have you seen any troop movements? If you have any information you would like to share with the BBC you can do so using the form below:
