SUBIC BAY NAVAL BASE, Philippines (AP) _ The captain of a U.S. Navy vessel ordered crewmen to keep Vietnamese refugees from climbing up the side of the ship, witnesses testifed Wednesday at the skipper's court-martial.

Capt. Alexander Balian, former skipper of the USS Dubuque, is accused of abandoning more than 80 Vietnamese refugees who allegedly resorted to cannibalism to survive.

Ensign Allen Esperum testified that Balian, 48, of Los Angeles, ordered him ''not to throw any life rings into the water'' when they encountered the boatload of refugees on Jan. 9 about 230 miles north of the Philippine island of Palawan.

A seaman apprentice, Jay Allen Philippsen, said he was at the port side of the upper deck when he saw the refugee boat and three Vietnamese with life preservers swimming toward the U.S. ship.

Philippsen said one of the swimmers managed to grab a monkeyline, a rope used to lower boats, and started climbing the vessel.

''Esperum ordered me to shake up the monkeyline,'' he said, adding that two sailors assisted him as he did so.

''The refugee who climbed up the monkeyline appeared to have a lot of strength. He splashed in the water, submerged and came up and tried to grab the monkeyline again,'' Philippsen said.

The three refugees later swam back to their boat when they saw two rubber boats from the ship approaching their craft with food supplies.

Petty Officer Benjamin Torango and seaman apprentice Charles Walag, who were both at the ship's deck, also testified that they saw the refugees try to climb aboard but were turned back. Torango said he was told to stay away from the deck afterwards.

Petty Officer Reid Bushard, meanwhile, said he was at the ship's pilot house at that time and that he heard Lt. Dan Steakley, the navigational officer, giving orders ''not to let any refugee aboard the ship.''

The prosecution says at least one Vietnamese drowned.

Balian is accused of violating navy regulations by failing to render necessary assistance to the refugees. A decorated Vietnam war veteran, Balian was relieved of command in August after Vietnamese survivors reported the encounter to U.N. officials in the Philippines.

United Nations officials say 31 of the Vietnamese perished before the others were rescued by Filipino fishermen June 27. Survivors said they devoured five of the dead, including two who were murdered.

Navy investigators recommended the court-martial of Balian. If convicted of all charges, Balian could be jailed for four and a half years, discharged dishonorably and ordered to forfeit all pay and allowances.

The trial began Friday when a six-member board of navy captains was empaneled to try the case.