Insurgents have blown up two trucks in the Iraqi town of Talafar, killing 50 people and injuring 125, police say.
George Bush said US forces had regained control in Talafar
One bomb was hidden in a truck that arrived at a market loaded with food supplies, and was detonated by the driver, a police spokesman said.
It was one of the largest attacks in Talafar since US President George Bush used the town to illustrate progress in Iraq, just over a year ago.
Other attacks took the day's death toll across Iraq to around 80.
They included an ambush which killed Sunni insurgent leader Harith al-Dari.
In other developments:
- Two elderly sisters - said to be nuns at Kirkuk's Cathedral of the Virgin - are reportedly stabbed to death in their home
- A mortar attack on the Shia enclave of Abu Chir in southern Baghdad leaves four dead, including two children, and 14 others wounded
- Four people die when gunmen open fire on a Sunni funeral cortege in Iskandariya, south of Baghdad, Iraqi army officials say
- The US military announces the arrest of two men it says are responsible for car bomb attacks accounting for 900 deaths in Iraq
The Talafar attack occurred when a truck arrived at the town's market, which has been suffering food shortages.
The driver was waved through and waited while hungry residents gathered round his truck, then exploded his bomb and obliterated them, a police spokesman said.
A second vehicle bomb caused further damage.
In a speech on 20 March last year, marking the third anniversary of the invasion of Iraq, Mr Bush spoke at length about the city of Talafar, which he said had been effectively liberated from al-Qaeda control.
It followed a joint Iraqi-US operation to root out insurgents during 2005, after which the town was surrounded with sandbanks to try to control entry and exit.
But the town, in the northern Iraqi province of Nineveh, near the Syrian border, has still been subject to attacks.
Ten people were killed when a man blew himself up outside a pastry shop in Talafar's market on Saturday.
Separately, at least 15 people were killed on Tuesday by a suicide car bomb outside the western city of Ramadi.
The attack is being seen as the latest episode in a continuing struggle between the Sunnis of Anbar province, says the BBC's Andrew North in Baghdad.
A car bomb attack in Ramadi may be linked to Sunni rivalry
It targeted a restaurant popular with local police, in an area where local tribes have formed an alliance against al-Qaeda.
In response there have been a series of attacks aimed at tribal figures and their supporters.
Another incident on Tuesday - the ambush and killing of an insurgent leader - was being linked to the same Sunni rivalry.
Harith al-Dari was a senior figure in one of Iraq's biggest Sunni Arab insurgent groups, the 1920 Revolution Brigades, and also the son of a tribal leader who had come out against al-Qaeda.
Meanwhile the US military announced that it had foiled a double truck-bomb attack on one of its bases west of Baghdad on Monday.
It said two trucks tried to ram their way into the base but were fired upon and blew up. Thirty insurgents attacked with small arms, rockets and mortars, but were repelled by US soldiers, a military statement said.
"Initial estimates indicate as many as 15 terrorists were killed," it said, adding that eight US soldiers were wounded.