Fierce clashes break out in Basra
Heavy fighting has erupted in Iraq's southern city of Basra amid a major pre-dawn offensive by Iraqi security forces against rival Shia militias.
Iraqi PM Nouri Maliki is in Basra overseeing the operation, a day after he vowed to "re-impose law" in the oil-rich city, the UK military said.
Eyewitnesses speak of plumes of smoke, explosions, tanks and artillery.
The British military, which returned control of Basra to the Iraqis in December, said it was not involved.
A spokesman for UK forces, now based only at Basra airport, said the operation was being directed entirely by Iraqi troops and that Mr Maliki was overseeing it from a military base at an undisclosed location in the city.
Security clampdown
Authorities in Basra have already imposed an indefinite night-time curfew because of the security situation.
The Iraqi army conducted raids across Basra on Tuesday, while routes into the city have been sealed off, according to reports.
Officials at the city's hospitals said a number of wounded people had been brought in.
A military official in Basra told Reuters news agency: "Basra is half empty. There are no vehicles and no one is going to work. People are afraid to go out."
After Monday's curfew was imposed, the powerful Mehdi Army warned it would retaliate if its members were targeted in any security clampdown.
The militia is loyal to radical Shia cleric Moqtada Sadr, who last month renewed a ceasefire the group had been observing since last August.
But it is reportedly in the middle of a turf war with rival Shia militias.
There have been a number of assassinations and kidnappings in its Basra stronghold.
Criminal gangs have been vying for control of lucrative oil-smuggling routes, say correspondents.
The oil fields in the Basra area are the source of most of Iraq's revenues.
The BBC's Adam Brookes says the operation appears to be aimed at loosening the grip of militias and criminal gangs on Iraq's most economically important city.
Yes, that's right folks, the Iraqi Army is doing the job the British one was supposedly doing for 5 years
EBC: Northeners, Huh! What are they good for?! Absolutely nothing!
Cybertron, Justice league...MM, HAB SDN City Watch: Sergeant Detritus
Days Unstabbed, Unabused, Unassualted and Unwavedatwithabutchersknife: 0