The death toll could rise as some bodies are thought to be buried beneath the rubble, and some people have been reported missing after the explosion, Ayan said.
Salaheddin is one of the provinces in which the US and Iraqi forces launched Operation Phantom Phoenix, a major offensive against al-Qaeda fighters which began on January 8.
Gates visit
The attack came as Robert Gates, the US defence secretary, arrived in Iraq to discuss security and to prepare talks on a pact that will define future relations between Washington and Baghdad.
Gates is to meet Iraqi officials as well as General David Petraeus, the head of the US armed forces in Iraq, to discuss a possible reduction of American troops.
"I will obviously be interested in hearing General Petraeus about his evaluation, where he stands and what more work he feels he needs to do before he is ready to come back with his recommendations," Gates told reporters travelling with him from Germany to Iraq.
Gates is due to give his recommendations to the US Congress in April about troop numbers in Iraq.
The defence secretary arrived in Iraq shortly before the one-year anniversary of the so-called surge designed to improve security in Baghdad.
The US military currently has a force of about 160,000 in Iraq.
Explosion of violence
Also on Sunday, fifteen people died after clashes broke out when armed men stormed the compound of an Awakening Council group in the town of Sinjir, west of Mosul.
Among those killed were 10 suspected al-Qaeda fighters and five members of the Sunni group which is supporting US and Iraqi forces in battling al-Qaeda.
A US military statement said that three civilians were killed and five injured in another attack by al-Qaeda fighters in Nineveh, but gave few other details.
Iraqi officials, meanwhile, said two policemen were killed and 10 wounded after a mortar attack on police headquarters in the central Iraq town of Balad Rooz.
In separate incidents in west Baghdad, one civilian was killed and two wounded in a drive-by shooting while two army officers were wounded in a gunfire attack on their car.