BAGHDAD, Iraq - American fighter jets flattened a suspected insurgent safe house near the Syrian border, the U.S. military said today, as hundreds of U.S. troops searched remote desert villages house by house for followers of Iraq's most wanted militant leader Abu Musab al-Zarqawi.

American forces have met little resistance since the first two days of Operation Matador, aimed at clearing a region believed to be a haven for foreign fighters slipping over the border from Syria, the military said in a statement today. American intelligence indicates the insurgents are either in hiding or have fled the region, U.S. Capt. Jeffrey Pool said in the statement.

Villagers reached by telephone today said gunmen still roamed some areas and they continued to receive U.S. shelling.

The U.S. offensive - one of the largest since militants were forces from Fallujah six months ago - comes amid a surge of militant attacks that have killed more than 420 people in just over two weeks since Iraq's first democratically elected government was announced.

A car bomb exploded in a jammed commercial district of the capital Thursday, setting cars, shops and restaurants ablaze in the most deadly of a string of attacks that killed 21 and injured more than 90. Iraqis expressed growing fury at the relentless bloodshed, throwing stones at police and U.S. forces who responded to the bombing that killed 17 Iraqis and injured 81.

Two more blasts rocked the capital today, both targeting American patrols, Iraqi police said. There were no immediate reports of casualties, but Associated Press Television News footage of the blasts showed a U.S. Humvee, its hood open, consumed by flames on a highway leading to the airport.

A 30-minute gunbattle erupted in Ghazaliyah, a nearby part of western Baghdad, when insurgents fired on Iraqi soldiers who were searching the area, said police Maj. Abdul Karim. There were no immediate reports of casualties.

Also in western Baghdad, snipers opened fire on the motorcade of the Interior Ministry's undersecretary Maj. Gen. Hikmat Moussa Hussein, killing one of his guards and wounding three, police Maj. Moussa Abdul Karim said. Hussein escaped unharmed.

North of the capital, a car bomb exploded today as an Iraqi army patrol was moving through Baqouba, killing three people and wounding six, police Col. Mudhafar Mohammed said. The dead included two soldiers and a civilian, he said.

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

"This requires patience," he said at a news conference Thursday. "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."

The U.S. military said information gained from a "senior terrorist" captured during the operation near the Syrian border led Marines to the safe house Thursday in Karabilah, a village about 200 miles northwest of Baghdad.

As Marines approached, at least four gunmen fired on them from the building, the military statement said. U.S. F-18 Super Hornet jets destroyed the building with a combination of bombs and rockets, the statement said.

The offensive was launched after U.S. intelligence showed large numbers of insurgents had moved into the northern Jazirah Desert following losses in Fallujah and Ramadi, further east.