BAGHDAD, Iraq (AP) – Al-Qaida in Iraq said Thursday it shot down a U.S. attack helicopter that crashed, killing two Marines, and a U.S. general said witnesses saw the aircraft take ground fire and break up in the air.

The AH-1W Super Cobra crashed Wednesday near Ramadi during daylong fighting in the insurgent stronghold 70 miles west of Baghdad. In addition to the two crewmen, an American lieutenant died when a bomb exploded as he was rushing to the crash site.

Another U.S. soldier died Thursday in a roadside bombing northeast of Baghdad, the military said.

In its statement, al-Qaida in Iraq, led by Jordanian terror mastermind Abu Musab al-Zarqawi, said that its military wing “downed a Super Cobra attack helicopter in Ramadi with a Strella rocket, thanks be to God.”

The authenticity of the statement could not be determined. It appeared on an Islamic Web site and bore the nickname of the group’s spokesman, Abu Maysara al-Iraqi. The U.S. military said the cause of the crash had not been determined.

However, Maj. Gen. Rick Lynch told reporters Thursday that witnesses “believe they saw a munition fired at the helicopter and saw the helicopter break in pieces in midair and then crash.”

In Burlington, Vt., Maj. Gen. Martha Rainville, the adjutant general of the state’s National Guard, said 2nd Lt. Mark Procopio, 28, of Burlington was killed Wednesday by the roadside bomb as his patrol of four Humvees and two tanks headed to secure the crash site.

“He and his patrol were on a routine mission when they saw a Marine helicopter coming under fire, realized it was going to crash, and responded to provide assistance as necessary and to secure the site,” Rainville said. The Humvee in which Procopio was riding struck the bomb and he was killed instantly, she said.

On Thursday, another U.S. soldier died in a roadside bombing near Baqouba, 35 miles northeast of Baghdad. The soldier’s name was not released, but the U.S. command said he was assigned to the Army’s 43rd Military Police Brigade.

The soldier’s death raised to at least 2,037 the number of U.S. military service members who have died since the war began in 2003, according to an Associated Press count.

It was also the eighth battle death among the 157,000-member U.S. force in November. October was the fourth deadliest month for American service members since the conflict began.

Roadside bombs, which the U.S. military refers to as “improvised explosive devices,” or IEDs, have accounted for most of the recent U.S. battle deaths, despite a vigorous campaign to improve armament on American vehicles and to hunt down insurgent weapons caches.

Last week, for example, 40 percent of the attacks against U.S. and coalition forces were carried out with IEDs, Lynch said. But they accounted for 64 percent of the U.S. and coalition casualties, he said.

Lynch declined to talk in detail about increased sophistication of roadside bombs, including the use of infrared triggers. British officials say they have seen the use of infrared triggers in attacks against their own forces and suspect the technology has been supplied by Iran, a charge the Iranians have denied.

“We have seen an improvement, an increase, in some instances of tactical capability of these IEDs and there are indeed different triggers, sensors that cause these things to explode,” Lynch said. “We have indications through multiple sources that bombs are transferred and technology is transferred and we’re working with all assets under our control to stop the flow of both of those things. … Neighbors need to be helpful and do their part to stop the insurgency.”

Lynch also predicted an increase in insurgent attacks in an attempt to derail the Dec. 15 elections, when Iraqis will choose a new parliament to serve for a full four-year term.

In a separate statement, al-Qaida in Iraq also said it had sentenced to death two Moroccan Embassy employees kidnapped last month in Iraq. The group had previously claimed the kidnap-slaying of three senior diplomats – one Egyptian and two Algerians – in a campaign to punish Arab countries for establishing ties with the U.S.-backed Iraqi government.

In other developments Thursday:

• Two Iraqi policemen were killed in a drive-by shooting in Baghdad.

• Bodies of 12 men who had been kidnapped and killed were found in a sewage station, police said. They were believed victims of sectarian “death squads” targeting members of rival Muslim sects.