Updated

Unidentified gunmen killed a parliamentary candidate and an Iraqi police commander in separate attacks Sunday while a bomb that detonated as a police patrol passed through central Baghdad killed three civilians, police said.

The latest attacks came one day after insurgents killed 19 Iraqi soldiers in a coordinated ambush northeast of Baghdad. On Thursday, the deadliest attack against U.S. Marines in four months killed 10.

U.S. and Iraqi officials have been warning of a surge in insurgent attacks ahead of national elections set for Dec. 15.

In the latest attacks, gunmen shot dead a Shiite Muslim candidate who was running in this month's general election. Sheik Abdul-Salam Abdul-Hussein, a follower of firebrand Shiite cleric Muqtada al-Sadr, died instantly in Baghdad's eastern neighborhood of Zayouna, police Lt. Bilal Ali said.

Gunmen in two cars opened fire on police commander Lt. Col. Abdul-Razaak Abdul-Jabbar as he was heading to work in western Baghdad, police Capt. Talib Thamir said.

The bomb exploded in Tahrir square, killing three civilians, police Cap. Nabil Abdelqadir said.

Saturday's attack occurred as an Iraqi army unit patrolled near Adhaim, about 60 miles north of Baghdad. Survivors said insurgents triggered a roadside bomb and then showered the patrol with rocket-propelled grenades and machine-gun fire.

The United States hopes a big Sunni turnout in the Dec. 15 elections will produce a government that can win the trust of the minority Sunnis, the backbone of the insurgency. Along with a stronger Iraqi military, it is hoped that will hasten the day when U.S. troops can leave.

President Bush said earlier this week that the eventual replacement of U.S. troops by Iraqi forces was key to his strategy for victory.