Friends and relatives of the attackers said they acted to avenge the killings of Palestinians by Israelis.
The two men — Anas al-Kandari, 21, and his 26-year-old cousin, Jassem al-Hajiri — opened fire Tuesday from a pickup truck on Marines engaged in urban assault training on Failaka, an island 10 miles east of Kuwait City, killing one Marine and injuring a second. After driving to a second location and attacking a second time, both Kuwaiti shooters were killed by Marines.
Kuwaiti authorities said Wednesday that they have detained four people as suspected co-conspirators in the attack, two U.S. defense officials said in Washington.
Violence continued to mar the U.S. military exercises in Kuwait. On Thursday, three U.S. Marines were injured in an apparent accidental explosion, a U.S. military spokesman said.
None of the injuries was believed life threatening, said Lt. Chris Davis at the U.S. Navy's Fifth Fleet headquarters in Bahrain.
"It seems to be an accident and we are investigating," Davis said.
U.S. and Kuwaiti officials labeled Tuesday's attack an act of terrorism. White House spokesman Ari Fleischer said links to Osama bin Laden's al Qaeda organization could not be ruled out. Officials were attempting to determine the extent of any such links.
Several Kuwaitis have been tied to bin Laden. Most notably, al Qaeda spokesman Sulaiman Abu Ghaith, who was stripped of his Kuwaiti citizenship in October 2001, and Kuwaiti-born Khalid Shaikh Mohammed, who is suspected of being a Sept. 11 mastermind.
Al-Kandari spent 18 months in Afghanistan, and his cousin al-Hajiri joined him there for six months, said Mohammed al-Awadi, a cleric who knew the men. Both returned days before the Sept. 11, 2001, terror attacks in the United States that are blamed on al Qaeda, the cleric said.
In a second incident, troops driving from Camp Doha to a site nearer the Iraqi border Wednesday said a man drove along side and pointed a gun at them. One of the Marines shot at the vehicle which veered off the road. Officials later said occupants of the civilian vehicle claimed only to have been holding a cell phone. No one was injured in the incident.
The Pentagon identified the slain Marine as Lance Cpl. Antonio J. Sledd, 20, of Tampa, Fla. The wounded Marine was identified as George Simpson, 21.
Al-Kandari was very moved by footage of Palestinians killed in the days before the attack, the cleric said. An Israeli raid Monday in the Gaza town of Khan Younis that left 16 Palestinians dead and more than 100 wounded has been heavily covered by Arab television.
"Every Muslim believes Americans are helping Jews, and he was burning to do something to help," Al-Kandari's brother, Abdullah, said.
Al-Kandari was born in 1981, his cousin in 1976, according to the Kuwaiti Interior Ministry.
The two attackers were buried Wednesday.
A member of al-Kandari's clan, though not a close relative, is among 12 Kuwaitis held by U.S. forces in Guantanamo Bay, Cuba, said Khaled al-Oda, who heads a non-governmental group campaigning for the prisoners' release.
On its Web site, the U.S. Embassy urged Americans in Kuwait to be vigilant.
Kuwait has been a Washington ally since a U.S.-led coalition liberated the emirate from Iraqi occupation in the 1991 Gulf War. More than a decade later, most Kuwaitis support the close relationship.
The military exercises, which resumed Wednesday and are called Eager Mace 2002, started Oct. 1 and involve 1,000 Marines and 900 Navy sailors.