The United States has warned Americans in Kuwait to be vigilant after the government detained suspected opponents of the coalition force in Iraq.

The U.S. Embassy urged Americans to be alert and try to avoid places where Westerners are known to congregate. There are some 14,000 American civilians in Kuwait and about 20,000 military personnel.

"With the detention of several individuals in Kuwait for suspected activities against the U.S. military in Kuwait and Iraq, the embassy would like to remind all U.S. citizens to be aware of their security posture at all times," the embassy said in a warden message distributed Monday.

Kuwait's government said this weekend that 11 people had been arrested and referred to prosecutors for their alleged roles in recruiting young Kuwaitis to fight the U.S.-led force in Iraq and other security charges.

Embassy spokesman Mark Stroh declined to provide information on the alleged threat to the U.S. military in Kuwait, but he praised the country's "swift action in these arrests."

"We continue to be pleased with the level of cooperation with Kuwaiti security forces," Stroh told The Associated Press.

Kuwait is a major ally of Washington. It was the launch pad for the invasion of Iraq that overthrew Saddam Hussein in April 2003. U.S. military personnel have been stationed in Kuwait since the 1991 Gulf War that ended Saddam's seven-month occupation of the country.

However, members of Kuwait's influential Muslim fundamentalist lobby opposed the war in Iraq and resent the U.S. military presence in their country.

A U.S. marine and an American civil contractor have been killed in attacks by extremists since 2002.