MANAMA, Bahrain (AP) _ U.S. Navy sailors trying to search a sugar-laden Iraqi ship in the Arabian Sea on Wednesday fired warning shots when crewmen and women peace activists tried to stop the search.

The boarding was the most chaotic among the thousands carried out by the U.S.-led multinational forces enforcing the U.N. trade embargo imposed to drive Iraq from Kuwait.

No injuries were reported in the 30-minute, predawn fracas in which British and Australian sailors backed up the helicopter-borne team from the USS Trenton.

Crew and passengers tried ''to hold the boarding party members back and grab their weapons,'' said a U.S. Navy spokesman, Cmdr. Mark Neuhart. ''They tried to physically block the way to the pilot house.''

Lt. Col. Greg Pepin told a military briefing in Saudi Arabia that the sailors fired pistols in the air as a warning and used smoke and noise-making grenades to control the crowd aboard the 11,333-ton vessel, the Ibn Khaldoon.

''It was more vocal than physical resistance,'' Neuhart said. He said the presence of the peace activists and some reporters might have contributed to problems with the boarding, near Masirah island.

Pro-Iraqi press reports refer to the Ibn Khaldoon as ''the peace ship,'' and say it was en route to the Iraqi port of Basra in a demostration of support for Saddam Hussein and his efforts to solve the Persian Gulf crisis.

The ship had an Iraqi crew of 40 as well as 240 passengers - mostly Palestinian and Iraqi women. Baghdad Radio, monitored in Nicosia, said women aboard were from 10 Arab countries, Italy, China, the United States and Japan.

Sailors who searched the freighter found it carried 800 tons of sugar and other cargo such as rice, cooking oil and milk, all prohibited under the U.N. trade embargo imposed to force Iraq from Kuwait.

The ship was later escorted to a nearby anchorage. Neuhart said the shipmaster agreed to divert the ship to an unidentified port to discharge the cargo. He said the passengers could then resume their voyage to Basra.

A doctor from the USS Trenton, an amphibious transport dock, was sent to the Ibn Khaldoon after the shipmaster claimed the boardings caused two heart attacks and two miscarriages, Neuhart said.

''The medical officer found no evidence to support the claims,'' he said. After consultations, the master agreed that there were no injuries.

Since the U.N. trade embargo went into effect, the U.S. Navy alone has challenged 5,888 ships, boarded 714 and diverted 30, mainly in the Arabian and Red seas. Pepin said that in 10 of the interceptions, warning shots were fired.

But ''the scuffling was somewhat unusual,'' he said of Wednesday's boarding.

The vessel, which gave its departure point as Aden, Yemen, was first intercepted by the Australian guided-missile frigate HMS Sydney early Wednesday but refused repeated requests to stop for a search.

The U.S. sailors were the first to board the ship when it did stop.

That team was backed up by sea-borne crews from the HMS Sydney, the USS Oldendorf and USS Fife. A British ministry of defense spokesman said Royal Marines from the HMS Brazen also descended onto the bridge of the Iraq vessel from a Lynx helicopter.