By Suadad al-Salhy
BAGHDAD (Reuters) - Iraqi forces stormed a Sunni Muslim protest camp on Tuesday, triggering a gunfight between troops and demonstrators that spread to army clashes with Sunni militants and killed more than 40 people.
The fighting was the bloodiest Iraq has seen since thousands of Sunni Muslims started staging protests in December to demand an end to perceived marginalisation of their sect by Prime Minister Nuri al-Maliki's Shi'ite-led government.
Sunni outrage and the violence across Iraq will only deepen already severe sectarian rifts in a country where Shi'ite and Sunni tensions simmer close to the surface just a few years after intercommunal slaughter killed tens of thousands.
Iraq's defence ministry said fighting erupted when troops opened fire early on Tuesday after coming under attack from gunmen during a raid on the makeshift protest camp in a square in Hawija, near Kirkuk, 170 km (100 miles) north of Baghdad.
"When the armed forces started... to enforce the law using units of riot control forces, they were confronted with heavy fire," the defence ministry said in a statement.
The defence ministry and military said troops found rocket-propelled grenades, sniper rifles, and other weapons. But protest leaders said they were unarmed when security forces stormed in and started shooting in the morning.
"When special forces raided the square, we were not prepared and we had no weapons. They crushed some of us in their vehicles," said Ahmed Hawija, a student.
The defence ministry said what is described as 20 gunmen were killed at the camp along with three of its officers. Military sources said 20 people and six soldiers died.
After the Hawija raid, security forces imposed a curfew in the surrounding province of Salahuddin, burned protesters' tents and cleared the square.
The United Nations envoy to Iraq called for talks to end violence and Maliki's office said it would set up a commission that included Sunni leaders to investigate the Hawija deaths.
But clashes inflamed tribal sensibilities in the Sunni Muslim heartland of western Iraq and violence spread with gunmen attacking army posts to the south of Kirkuk. At least 13 gunmen were killed in attacks, a ministry of defence official said.
Three soldiers were killed during clashes with protesters who attacked a passing army convoy and militants burned two army Humvees on the highway outside Ramadi, 100 km (60 miles) west of Baghdad, according to local authorities.
In a village outside Tuz Khurmato, 170 km (105 miles) north of the capital, militants used a mosque loudspeaker to call Sunnis to mobilise before clashing with troops, officials said. Four soldiers and one insurgent were killed in the fighting.
Throughout the day, mortar attacks, bombs and gunmen also killed at least 21 worshippers as they left two Sunni mosques in Baghdad and another in Diyala province in the north, according to police and medical sources.
The Hawija raid and ensuing violence will likely worsen divisions in Maliki's government which has been deadlocked by fighting among Shi'ite, Sunni and ethnic Kurdish parties over how to share power since the last American troops left in 2011.
Iraq's education and science and technology ministers, both Sunni Muslims, offered to resign on Tuesday in protest over the Hawija incident, according to the deputy prime minister's office and their Iraqiya party.
Since the last U.S. troops left, Iraq's government has been mired in crisis over the power-sharing agreement along sectarian and ethnic lines. Maliki's critics accuse him of amassing power at their expense.
Many Iraqi Sunnis say they were sidelined after the U.S.-led 2003 invasion that ousted Sunni strongman Saddam Hussein and allowed the Shi'ite majority to gain power through elections.
Tuesday's fighting broke out shortly after a weekend provincial election that was the first in Iraq since U.S. troops withdrew. But voting was suspended in two predominantly Sunni provinces.
Violence has eased since the slaughter that erupted after al Qaeda militants bombed an important Shi'ite shrine in 2006 and triggered a wave of retaliation by Shi'ite militias against Sunni communities, but still claims dozens of lives.
On Tuesday, at least 10 worshippers were killed when mortar rounds landed on a Sunni mosque in Muqdadiya in Diyala province, 80 km (50 miles) northeast of Baghdad, police and medical sources said.
Earlier, two bombs killed seven people outside a Sunni mosque in southern Baghdad and police said gunmen killed four worshippers as they left prayers held in a Sunni mosque in an eastern district of the capital.
(Additional reporting by Kareem Raheem and Ahmed Rasheed in Baghdad and Gazwan Hassan in Samarra; Writing by Patrick Markey; Editing by Michael Roddy)