The United States suffered its first combat casualty during Operation Iraqi Freedom on Friday when a U.S. Marine was killed.

The slain soldier, of the 1st Marine Expeditionary Force, was part of the ground assault in southern Iraq, said Lt. Col. Neal Peckham, a British military spokesman in Kuwait.

According to a comrade, the Marine was shot in the stomach while his company was sweeping around a burning oil pumping station.

Military officials said the soldier died in the advance on the Rumeila oil field.

The identity of the Marine was withheld until next of kin is notified.

"There has been a Marine killed in action. I have no other details. We are still collecting information," said chief of the media center at U.S. Central Command in Qatar, Captain Frank Thorpe, reports Reuters.

The incident came hours after eight British and four U.S. soldiers died in a U.S. Marine helicopter crash. A British military spokesman said the crash was an accident.

The crash happened as U.S. Army and Marine units, joined by their British comrades in arms, surged across the Kuwaiti border into southern Iraq on Thursday and Friday, working at first to secure the region's oil wells, several of which had been set afire.

President Bush was informed "first thing this morning" about the military personnel fatalities by National Security Adviser Condoleezza Rice, a senior administration official told Fox News.

The president, the official said, expresses his "sympathies and condolences to the families of those involved." The official added: "This is a reminder to the American people that this is war."

Fox News' Mike Emanuel and James Rosen and The Associated Press contributed to this report.