Baghdad, Iraq ? Iraqis unleashed their fury at weeks of relentless bloodshed Thursday, throwing stones at police and U.S. forces they accused of failing to protect them at the scene of a car bomb that set buildings and vehicles ablaze in the middle of a jammed commercial district.

The unexpected protest by Baghdad residents followed a wave of attacks that have killed more than 420 people in the two weeks since Iraq’s first democratically elected government was announced.

The blast at a busy intersection was the deadliest in a string of attacks Thursday that killed at least 21 Iraqis, including an army general and police colonel gunned down on their way to work, and left more than 90 injured.

The violence came as U.S. troops were in the midst of a major offensive near the Syrian border, 200 miles northwest of Baghdad. Fierce clashes were reported with insurgents on the outskirts of the town of Qaim, where angry residents lashed out at U.S. forces.

“They destroyed our city, killed our children, destroyed our houses. We have nothing left,” one man in Qaim told Associated Press Television News. He did not give his name and hid his face with a scarf to address the camera.

Families were fleeing in trucks packed with luggage and APTN footage showed plumes of smoke rising from the town. U.S. forces pounded the area with air strikes, artillery barrages and gunfire in the first days of the offensive aimed at rooting out followers of Iraq’s most wanted militant leader, Abu Musab al-Zarqawi.

Five more American troops died in Iraq, two during the offensive Wednesday and three others when their convoys hit roadside bombs Thursday in Baghdad and surrounding areas, the U.S. military announced.

At the Pentagon, Gen. Richard Myers, chairman of the Joint Chiefs of Staff, indicated Thursday the insurgency could last for many more years.

“This requires patience,” he said at a news conference. “This is a thinking and adapting adversary. … I wouldn’t look for results tomorrow. One thing we know about insurgencies, that they last from three, four years to nine years.”

An Iraqi man stands atop a burned-out car as he tries to calm the crowd after a car bomb exploded near a market in eastern Baghdad, Iraq. Thursday's attack killed at least 17 people and wounded 81, police said.

“What we’re seeing is really an attempt to discredit this new Cabinet and new government,” Myers said. “This is, the most cases, Iraqis blowing up other Iraqis. And I don’t how they expect to curry favor with the Iraq population when we have Iraqi-on-Iraqi violence.”

Scores of Iraqis in Baghdad vented their frustration at the nonstop violence, beating two Iraqi photographers and throwing rocks at Iraqi police and U.S. forces at the site of the bloody car bombing near a market, cinema and mosque.

The U.S. and Iraqi troops fired in the air to disperse the crowd.

The blast killed 17 Iraqis and injured 81, including women and children, police said. About 15 minutes later, the fuel tank of a burning car also exploded, wounding three more people.

In all, four car bombs hit Baghdad on Thursday, two of them suicide attacks, said Master Sgt. Greg Kaufman, a U.S. military spokesman.