WASHINGTON — A Yemeni portrayed as a Qaeda operative and a member of a terrorist family confessed to plotting the bombings of the USS Coleand two American embassies in Africa, killing hundreds, according to a Pentagon transcript of a Guantanamo Bay hearing.

The transcript released yesterday was the fourth from the hearings the military is holding in private for 14 “high-value” terror suspects who were kept in secret CIA prisons before they were sent to the American facility in Cuba last fall.

Last week, Waleed bin Attash said he helped plan the 1998 embassy bombings in Kenya and Tanzania that killed more than 200, according to the transcript. He also said he helped organize the 2000 attack on the USS Cole in which suicide bombers steered an explosives-laden boat into the guided-missile destroyer, killing 17 sailors.

Legal experts have criticized the American decision to bar independent observers from the hearings, called combatant status review tribunals. Carl Tobias, a University of Richmond law professor, said “legitimate criticisms can be raised” about the confessions coming out of the hearings.

“Of course, no one’s there to know, other than what we see from the transcripts and what the hearing officers hear,” Mr. Tobias said.

“The claim has been that some of the confessions were extracted by torture or other activities that are inappropriate, and [there are] doubts about whether the detainees are telling the truth,” he said.

Many have questioned the confession of Khalid Sheikh Mohammed, also known as KSM, who claimed responsibility or partial responsibility for nearly three dozen plots including the 9/11 attacks on the U.S., according to transcripts of his March 10 hearing released last week.