Several bombs exploded nearly simultaneously Tuesday in a mainly Shiite area in Baghdad, killing at least eight people and raising fears of a sustained insurgent campaign aimed at provoking new sectarian tensions.

The blasts raised the five-day death toll to 115 in the worst spasm of violence the country has suffered since U.S. forces left the cities on June 30, turning over urban security to Iraqi troops.

An explosives-laden car and two other bombs detonated within minutes of each other at about 8:40 p.m. in the Amin al-Thaniyah neighborhood in eastern Baghdad, killing at least eight civilians and wounding 22, according to police and hospital officials.

Another bomb exploded about 20 minutes later some 900 meters from the initial blasts, wounding five people, a police officer said.

The officials all spoke on condition of anonymity because they weren't authorized to release the information.

Attacks in Mosul, which the U.S. military has called the last stronghold of Al Qaeda, also killed at least 34 people Monday and 44 on Friday. It was the first time since the U.S. turned urban security over to the Iraqis on June 30 that insurgents have managed to stage two massive attacks in short order.

The explosions Tuesday in Baghdad appeared to have a lower death toll but heightened concerns about security measures in the capital because they came after 29 people were killed in a spate of bombings, also on Friday and Monday, in Baghdad.

Nobody claimed responsibility for the attacks, but car bombings and homicide attacks bear the hallmark of Al Qaeda in Iraq.

The U.S. military has warned insurgents will step up efforts to re-ignite sectarian violence but have said the Shiites so far have shown restraint. Ethnic tensions between Arabs and Kurds also are high in northern Iraq.

The bloodshed threatened to chip away at public confidence in the U.S.-backed government as it seeks to project a sense of normalcy ahead of next year's national elections, including an announcement last week that all concrete blast walls will be gone from Baghdad's main roads by mid-September.

The Iraqi government has responded to the recent attacks by tightening security at checkpoints and mosques, and stepping up searches as the sustained violence raised concern over the ability of Iraq's security forces to safeguard the population as U.S. forces prepare to withdraw by the end of 2011.

"Our security troops have increased the number on the streets," said Iraqi army Capt. Majid Kadhim. "Yesterday there were security violations. God willing, our forces are ready to safeguard people."