Iraqi troops arrested on Saturday leading Sunni MP Ahmed al-Alwani in a raid on his home in the western city of Ramadi, killing his brother and five guards.
Another 18 people were wounded during the raid.
"Security forces attacked the residence of MP Ahmed al-Alwani in central Ramadi to arrest him this morning, sparking a battle with his guards with automatic weapons and rocket-propelled grenades," a police major said.
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"Five of Alwani's guards and his brother were killed and eight others wounded, while 10 security forces members were also wounded," the major said.
Alwani had supported protests against Prime Minister Nouri al-Maliki's mainly Shia government and was reportedly wanted on terrorism charges.
His violent arrest is expected to worsen tensions in Sunni-dominated Anbar province, where the protests have been taking place.
Maliki earlier this month said the protest site near Ramadi had become a headquarters for Al-Qaeda and called on protesters to leave.
More protests occurred in the Sunni majority areas of Iraq last year after Rafa al-Essawi, another prominent Sunni politician, was arrested on terrorism charges.
Since the beginning of this year, more than 6,700 people have been killed in sectarian violence in Iraq.