Iraqi security forces on Saturday raided the home of a Sunni MP who backs anti-government protesters, arresting him and sparking clashes that killed his brother and five guards, police said.
The raid threatens to inflame widespread discontent among Iraq's Sunni Arab minority and could compound rampant violence plaguing the country.
A police major said automatic weapons and rocket-propelled grenade launchers were fired in the clashes that erupted during the raid on MP Ahmed al-Alwani's home in Ramadi, west of Baghdad.
Alwani's brother and five guards were killed, while 18 people, including 10 security forces members, were wounded, according to two police officers and a doctor from the Ramadi hospital.
The defence ministry said Alwani's brother Ali, who was wanted on terrorism charges, was the target of the raid, which took place at about 4:00 am (0100 GMT).
When security forces arrived, the two brothers and their guards opened fire, killing one security forces member and wounding five, said a ministry statement.
Ali and two guards were wounded and taken to hospital, while Ahmed was arrested.
A blurry image of Ahmed al-Alwani, his head down and his face apparently bruised, was posted on the Iraqi special forces' Facebook page, with a caption indicating he had been arrested by counter-terrorism forces.
Hundreds of people armed with automatic weapons protested at Alwani's home in Ramadi after the raid, an AFP journalist said.
"With soul, with blood, we sacrifice for you, doctor," they shouted, referring to the MP.
Speaker questions legality of arrest
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Parliament speaker Osama al-Nujaifi, a Sunni, sharply criticised the arrest and described it as "treading on the core of the Iraqi constitution and a clear violation of its articles".
Nujaifi said in a statement that MPs have immunity and added he was dispatching a parliamentary delegation to Anbar province, where the raid occurred, to investigate the case.
However, the constitution says MPs can be arrested without parliament waiving immunity if they are caught committing a serious crime, which security forces may argue in Alwani's case.
Alwani, in his 40s and serving his second term as an MP, is a well-known supporter of Sunni Arab anti-government protesters camped on a highway near Ramadi, and has frequently spoken at the site.
Protests broke out in Sunni Arab-majority areas of Iraq late last year after the arrest of guards of then-finance minister Rafa al-Essawi, an influential Sunni Arab politician, on terrorism charges.
The arrests were seen by Sunnis as just the latest example of the Shiite-led government targeting one of their leaders.
In December 2011, guards of vice president Tareq al-Hashemi, another prominent Sunni politician, were arrested and accused of terrorism, while he fled the country and has since been given multiple death sentences for charges including murder.
The demonstrations have tapped into long-standing grievances of Sunnis, who say they are both marginalised by the Shiite-led government and unfairly targeted with heavy-handed tactics by security forces.
Iraqi Prime Minister Nuri al-Maliki, a Shiite, meanwhile said on December 22 that the protest site near Ramadi had become "a headquarters for the leadership of Al-Qaeda," giving those not affiliated with the group a "very short period" to leave before security forces move in.
Sunni discontent has been a key factor in the sharp surge in violence in Iraq this year, boosting recruitment for militant groups, pushing them to carry out attacks and eroding cooperation with security forces.
But while the government has made some concessions aimed at placating Sunni Arabs, including freeing prisoners and raising the salaries of anti-Al-Qaeda fighters, underlying issues remain unaddressed.
The last major security operation at a protest site, near the northern town of Hawijah on April 23, sparked clashes in which dozens of people were killed.
Nationwide death tolls from violence then spiked, reaching a level not seen since 2008, when the country was just emerging from a brutal period of sectarian killings.
The violence continued on Saturday, with attacks by suicide bombers and gunmen killing eight people in Iraq, among them four police and two soldiers, and wounding 11.
More than 6,700 people have been killed in violence since the beginning of the year, according to AFP figures based on security and medical sources.