BAGHDAD, Iraq — A U.S. Marine attack helicopter crashed today near Ramadi, killing two crew members, after insurgents fought with American ground forces in the city and destroyed at least one of their Humvees, police said.

The day before, a Marine and a sailor died in the city 70 miles west of Baghdad when their vehicle was hit by a roadside bomb, the U.S. command said.

Associated Press Television News video from the streets of Ramadi showed a burning civilian vehicle and what appeared to be the wreckage of the destroyed Humvee.

A crowd of Iraqis gathered at the site, and one man, who waved a damaged machine gun in the air, said the attacks caused U.S. casualties. Police Capt. Nassir al-Alousi said insurgents used guns, rockets and roadside bombs to attack U.S. patrols late Tuesday.

The U.S. military in Baghdad said it had no immediate information of ground fighting in Ramadi on Tuesday night or this morning.

But the U.S. command said the AH-1W Super Cobra went down about 8:10 a.m. near Ramadi, killing the two crew members.

The military said the cause of the crash was being investigated. APTN quoted another Iraqi man who said he saw the crash and that insurgents "fired at the helicopter and shot it down."

Both Iraqi men refused to give their names because they feared for their safety. Fighting between coalition forces and insurgents is common in Ramadi.

Later today, a Marine F-18D fighter jet dropped two 500-pound bombs on what the military described as a reported insurgent command center near where the Cobra had crashed. It was not known whether there were any casualties.

In other violence today, 11 Iraqis were killed and 23 wounded by a car bomb, three roadside bombings and seven drive-by shootings. Most of the violence occurred in the capital.

In the worst attack, a roadside bomb aimed at a U.S. military convoy south of Baghdad hit a minibus instead, killing five Iraqis, police said.

The U.S. command also announced it was stepping up counterinsurgency training for newly arrived officers to help them protect patrols from such attacks.

The New York Times reported that the school will be for newly arrived Army and Marine officers and allow field commanders to give them the latest tactics on finding and destroying roadside bombs and dealing with Iraq's many insurgent factions.