President Nixon ordered that Lt. William L. Calley Jr. be released from prison immediately last night pending a review of his court martial, as North Vietnamese troops made another devastating attack on South Vietnamese outposts near the Laotian border.

Nixon's order was made in response to growing sentiment against Calley's conviction, as evidenced by mail received at the White House, said Presidential press secretary Ronald Ziegler.

Nixon has already received 5000 telegrams and there is a backlog of 20,000 waiting to be transmitted. They are running 100 to 1 in support of Calley, Ziegler said.

News of Nixon's action drew applause and cheers from members of the House who were in the middle of a debate on extension of the draft.

There is nothing irregular in keeping a defendant free until a final decision is made, said John Roemer, executive director of the Maryland American Civil Liberties Union. "Calley is no exception; I see no reason why he shouldn't be released pending a review," Roemer said.

Calley, 27, was convicted Monday by a military jury at Ft. Benning, Ga., of the premeditated murder of at least 22 Vietnamese old men, women and children at My Lai. He was sentenced to life imprisonment at hard labor.

Meanwhile, the U.S. Command in Saigon reported 56 American combat deaths last week, the highest in a month, and 542 Americans wounded, the highest in six months.

Retaliation

North Vietnamese troops made a third major attack yesterday in apparent retaliation for Saigon's drive on supply lines in Laos. The attack began at dawn Wednesday on Fire Base No. 6, located six miles east of the Lacsian border. Latest reports indicate that the base is still being contested.

Although no immediate report concerning U.S. advisers was made by allied officials, an NLF broadcast said U.S. advisers had been captured along with South Vietnamese troops.

South Vietnamese troops made yet another drive into Laos and destroyed 12 huts and a quantity of foodstuff and ammunition, according to Lt. Col. Le Trung Hien. The attack was disclosed Wednesday night by South Vietnamese President Nguyen Van Thieu.