Police said 140 people were wounded in the suicide bombing, one of several attacks in recent weeks targeting Shi´ite religious gatherings. The provincial governor, Atheel al-Nujaifi, said 37 people died in the attack and 276 were wounded.
A week ago a series of blasts outside Shi´ite mosques in Baghdad killed 31 people. Sunni Islamist militants like al Qaeda, who consider Shi´ites heretics, are often blamed.
"I was in the house when this explosion happened. I hurried to the mosque to search for my father in the ruins...I found him seriously wounded, and took him to hospital, but he died," said Khalil Qasim, 19, crying.
Mosul authorities urged citizens to donate blood and appealed for construction vehicles to lift debris trapping victims of the attack, which took place in Shreikhan, a majority Shi´ite Turkmen village just north of Mosul city.
Bombings and shootings are reported almost daily in Mosul.
The insurgency in Iraq has waned in the last 18 months, but insurgents have been able to hide out in the mountainous areas around Mosul, 390 km (240 miles) north of Baghdad, and have exploited divisions between Mosul´s feuding Arabs and Kurds.
The dispute in the northern province of Nineveh, of which Mosul is the capital, threatens to split the province and inflame tensions that could threaten Iraq´s long-term stability.
"There are parties that seek to create chaos inside Mosul by dragging Iraq into sectarian fighting," Nujaifi said.
In other Mosul violence, police said gunmen shot dead an off duty policeman. Gunmen also killed two policemen when they opened fire on a police checkpoint southeast of the city.
SQUARE ONE
Many Iraqis also fear attacks on Shi´ites may re-ignite the sectarian slaughter between Sunnis and Shi´ites that peaked in 2006-2007. Tens of thousands have been killed in the bloodshed since the U.S.-led invasion more than six years ago.
"These bombings are an attempt to return Iraq to square one," said analyst and professor Hameed Fadhel.
"I expect these attacks to rise the closer we get to the elections. The coming months will be a very critical time for Iraq," he added, referring to national polls due in January.
Politicians are in the throes of discussing coalitions, and violence may make cross-sectarian alliances difficult.
In Baghdad, roadside bombs exploded as minibuses carrying Shi´ite Muslims home from pilgrimage a day earlier passed by.
Roadside bombs struck two minibuses in separate incidents in the poor Baghdad Shi´ite district of Sadr City and another roadside bomb struck a minibus in east Baghdad, a hospital source said, killing a total of six and wounding 24.
In what could be an echo of previous tit-for-tat sectarian attacks, a bomb hidden in a motorbike later killed six people and wounded 35 in a mostly Sunni district of west Baghdad.
Several large-scale attacks in recent weeks have raised doubts about the Iraqi security forces´ ability to cope alone after U.S. combat troops withdrew from urban centers in June.
However, a Shi´ite pilgrimage of hundreds of thousands in the holy city of Kerbala on Thursday passed largely peacefully, as did an earlier religious gathering of millions in July.
Pilgrims poured into Kerbala to mark the birth of Imam Mohammed al-Mehdi, a Messiah-like figure Shi´ites believe vanished centuries ago and will return to bring peace on earth.
(Additional reporting by Muhanad Mohammed, Waleed Ibrahim and Khalid al-Ansary in Baghdad.
Related story
Bombing near Shiite place of worship kills 22 in NW Pakistan
