A teenage gunman killed the head of the Iraqi parliament's biggest Sunni bloc on Friday, police and a party officials said, adding four others were killed in the grenade and gun attack in a mosque in Baghdad.
Another 12 people were wounded and the gunman, who witnesses said appeared to be around 15 years old, was killed as he tried to flee the scene.
The slain lawmaker was identified as Harith al-Obaidi, who was head of the Accordance Front and also a member of the parliament's human rights committee.
"A young man entered the mosque, shot down the MP and his bodyguard, and then threw a grenade that killed four people and wounded 12," an interior ministry official said.
The attack occurred in the al-Shawaf mosque in al-Yarmuk, western Baghdad, after Friday prayers, which Obaidi was leading, on the Muslim holy day of the week.
The motive for the killings was not immediately clear.
In two other attacks, one in Baghdad and the other northeast of the capital, three people, including a teenage girl, were killed and 11 wounded, two days after Iraq's bloodiest attack since May 20.
Obaidi, born in 1966, was deputy chairman of parliament's human rights committee and on Thursday had called for an independent inquiry into torture and abuse of detainees in Iraq's prisons.
Salim Abdullah al-Juburi, spokesman for the National Concord Front, said the gunman had targeted "honest people who were fighting for others' rights," but added the party did not have any information about who was behind the attack.
The head of the Islamic Party, Osama al-Tikriti, described Obaidi as a "national symbol" and a strong "voice in parliament for human rights."
Iraq has seen several political assassinations since the American-led invasion of 2003.
In February, Islamic Party official Samir Safwat was killed outside his Baghdad home by gunmen in a car. A month earlier, two candidates standing in provincial elections held on Jan. 31 were killed in Baghdad and Mosul.
Friday's attacks come less than three weeks before the June 30 withdrawal of U.S. troops from Iraq's urban centers, as part of an accord between Baghdad and Washington which will see all U.S. combat troops leave Iraq by the end of 2011.
Prime Minister Nouri al-Maliki warned on Thursday that insurgents and militias would likely step up their attacks in the coming weeks in a bid to undermine confidence in Iraq's own security forces.