BAGHDAD - The government yesterday blamed al-Qaeda in Iraq for killing a prominent Sunni lawmaker as leaders across the sectarian divide rallied together, deploring the murder and pledging to prevent a new wave of religious violence that once sent the nation to the brink of civil war.

Harith al-Obeidi, leader of the largest Sunni bloc in Parliament, and his bodyguard were shot dead Friday as they left a Baghdad mosque after prayers. The gunman died when he triggered a grenade as he was chased by police and mosque guards.

No group claimed responsibility for the brazen attack, which could threaten efforts to reconcile the country's rival ethnic and religious communities.

The Interior Ministry spokesman, Maj. Gen. Abdul-Karim Khalaf, said evidence so far pointed to al-Qaeda in Iraq, a Sunni terror network that frequently targets fellow Sunnis who speak out in favor of national reconciliation.

Al-Obeidi was also an outspoken champion of the rights of detainees, most of whom are Sunnis, but also include Shiite militants.

The day before his death, Obeidi called on Parliament to summon officials from the interior and defense ministries to respond to the allegations of widespread beatings and torture in Iraqi jails.

That raised suspicion that his slaying may have been linked to his campaign on behalf of detainees. Some politicians suggested that Saddam Hussein loyalists might have been involved in a bid to undermine the government.

Whoever was responsible, the slaying of a figure who had been prominent in Sunni political circles for years raised the specter of renewed tit-for-tat sectarian killings in a culture steeped in a tradition of vendetta killings.

Fears of sectarian warfare have increased with a series of bombings this year against Shiite civilians. A car bomb Wednesday killed about 30 people in a small Shiite town near Nasiriyah that had largely been spared of violence.

Mindful of the dangers, the Iraqi Parliament convened a special session yesterday to honor Obeidi with a nationally televised funeral at Baghdad's Convention Center in the guarded Green Zone.

Speaker after speaker - Shiites, Sunnis, and Kurds - took the podium to express outrage over the killing, to praise Obeidi for efforts on behalf of reconciliation, and to pledge to prevent a new sectarian war.