Marines near the border on Saturday fired the heaviest artillery barrage of the war with Iraq, shelling Iraqi positions six miles inside occupied Kuwait.

The Pentagon reported three Marines killed and seven injured in a two-vehicle accident related to the operation.Commanders at the 1st Marine Division headquarters said three batteries of 155mm howitzers fired on Iraqi positions near the L-shaped section of Kuwait's border with Saudi Arabia.

The Marines have moved up to the border and fired howitizers twice before, but a news-pool report from the scene said officers described Saturday's barrage as the biggest yet.

In the previous attacks, only one battery was fired. A battery normally consists of eight guns.

An Iraqi vehicle was reported destroyed in a brief firefight along the border during the Saturday operation.

In Washington, the Pentagon said late Saturday that the three Marines were killed when two light armored vehicles collided. The Pentagon said seven soldiers were injured, and four of them evacuated by helicopter.

The three dead were identified as Pfc. Michael A. Noline, 20, of Phoenix, Ariz.; Staff Sgt. Michael R. Conner, 32, of Fremont, Calif.; and Lance Cpl. Arthur O. Garza, 20, of Kingsville, Texas.