Five Bahraini men aged 31-41 were arrested for plotting terrorist acts against the island's "national interests and endangering the lives of innocent people," the official Bahrain News Agency reported.
Police also seized weapons and ammunition that the detainees were planning to use "for carrying out acts of terrorism targeting the security of the country and the people," the agency reported.
Bahraini officials, speaking on condition of anonymity, said the arrests - the first terror-related detentions inside this close U.S. ally since Sept. 11 - occurred in the past two days.
It was not clear if the men were part of a larger terrorist network.
With anti-American sentiment growing in the Gulf region over a threatened U.S. war on Iraq, military planners are alert to possible attacks like the 2000 suicide bombing of the USS Cole in Yemen, which killed 17 U.S. sailors.
Last month, U.S. Navy chiefs deployed high-speed Navy patrol cutters to the Gulf to protect U.S. military ships, oil tankers and command vessels.
Bahraini officials said investigations into the terror suspects were ongoing and declined to give details about whether there was a specific plot. One official said the investigation would include whether U.S. naval facilities were a target.
Bahrain hosts 4,000 American military personnel and may play a role in any U.S. attack on Iraq.
When U.S. officials raised the terror alert level from yellow to orange recently, intelligence that attacks were being planned on American interests overseas, particularly military personnel in the Gulf region, were cited as one of the reasons.
Separately, CBS News correspondent Cami McCormick reports there was an anti-war demonstration in Bahrain, outside the UN House, as part of the worldwide anti-war protests Saturday. The protestors chanted "No to war" and "Save Iraqi children."
McCormick says the rally made the front page of at least one newspaper, along with an editorial that says the price of a war with Iraq is not something that will be paid off easily.