Washington ? One U.S. Marine was killed and another injured Tuesday in Kuwait when two gunmen in a pick-up truck fired on them with assault weapons during an urban warfare exercise.

In what the Kuwait government described as a terrorist act, two Kuwait citizens fired on the Marines during a U.S.-Kuwait live-fire training session on remote Failaka Island, 10 miles off the mainland in the Persian Gulf. The gunmen were killed when they sped ahead in their truck and fired on a second group of Marines, who returned fire.

Kuwait officials would not discuss whether the gunmen were connected to Muslim or Iraqi-backed extremist groups, but the shooting occurred at a time when President Bush and administration officials have increased the pressure for military action to remove Iraqi leader Saddam Hussein, who invaded Kuwait in 1991.

An Interior Ministry statement said “this is a terrorist act” and Kuwait’s government “will not allow anyone to undermine the country’s security.”

The identity of the Marine who died was being withheld until his family could be notified. Pentagon spokeswoman Victoria Clarke said the Marine was evacuated from Failaka Island and died during surgery in a hospital unit at Camp Doha, the American military base near Kuwait City.

The second Marine sustained a gunshot wound to his arm, according to Navy Lt. Cmdr. Nick Balice of the U.S. Central Command, which is responsible for U.S. military operations in the Persian Gulf region.

All the Marines in the exercise were removed from Failaka Island after the shooting, but they will return today to continue their training, according to Navy Lt. Daniel Hetlage

Kuwait’s Interior Ministry identified the two dead gunmen as Anas Ahmad Ibrahim Al-Kandari, 21, and Jassem Mubarak al-Hajri, 27. Both were wearing civilian clothing when they entered the military exercise area and opened fire.

The bodies of the gunmen were turned over to Kuwaiti authorities, Balice said. Three AK-47 assault rifles and a supply of ammunition were found in the truck, according to the U.S. Fifth Fleet in Bahrain.

Balice said it was unclear how the two men gained access to the exercise area. “Typically when we do exercises like this, the area is excluded,” Balice said.

Thirty-one other civilians on the island at the time of the shooting were held for questioning.

Failaka Island was inhabited by more than 2,000 Kuwaitis before the gulf war, and featured vacation homes, farms and a resort. But the Kuwait government moved its residents to the mainland during the fighting, and the island has remained largely off limits since then, according to a Taraq Almezram, a Kuwait Embassy spokesman in Washington.

“You must get clearance from the Ministry of Interior, the Ministry of Defense,” Almezram said. “If you have property then you can go by getting clearance, and many people still own property there.”

A 1,000-strong Marine element arrived in Kuwait last month to take part in Operation Eager Mace, a nearly annual exercise since the 1991 war. The Marines are members of the 11th Expeditionary Unit from Camp Pendleton, Calif. They were deployed to the island from two Navy amphibious transport ships, the USS Denver and USS Mt. Vernon.