NEW YORK – Two high school classmates of admitted terrorist Najibullah Zazi were indicted Thursday in a foiled scheme to bomb New York City subways that a prosecutor said was directed by "al-Qaida leadership.

Zarein Ahmedzay and Adis Medunjanin, both 25, pleaded not guilty in federal court in Brooklyn to charges of conspiracy to use weapons of mass destruction, conspiracy to commit murder in a foreign country and providing material support to the al-Qaida terrorist network.

Zazi, a former Colorado airport shuttle driver who attended high school in Queens, pleaded guilty to similar charges this week. Zazi was arrested in September after he drove cross-country from Denver to New York, where authorities said he abandoned the bombing plan after realizing authorities were watching him.

Ahmedzay and Medunjanin are accused of plotting "three coordinated suicide bombing attacks" on Manhattan subway lines that were timed for one of three days after the eighth anniversary of the Sept. 11 attacks, at the beginning of the work week, Assistant U.S. Attorney Jeffrey Knox said.

The attacks were planned to resemble the July 2005 bombings on the London transit system, Knox said. Four suicide bombers killed 52 people and themselves in an attack on three subway trains and a bus in London.

The operation was "undertaken at the direction and under the control of al-Qaida leadership," Knox said.

During the short hearing, U.S. District Judge Raymond J. Dearie asked prosecutors if they expected more defendants in the case. "Likely, although probably from overseas," Knox responded.

Police Commissioner Ray Kelly said this week that Zazi and two other bombers planned to kill as many people as possible. He didn't name the two other suspects but said the plot had been disrupted.

Authorities have said the plot was one of the most serious terrorism threats in the U.S. since the 2001 terrorist attack.

This attack would have been deadly," Attorney General Eric Holder said.

Authorities have told The Associated Press that Zazi was cooperating with federal investigators before his guilty pleas this week. Asked whether Zazi would testify against his client, Ahmedzay's attorney Michael Marinaccio said: "That's a likely scenario.

Medunjanin and Ahmedzay — who authorities say traveled to Pakistan with Zazi in 2008 to join the Taliban — had already faced charges in the alleged plot.

Medunjanin has pleaded not guilty to charges he conspired to kill U.S. soldiers in Afghanistan. His lawyer, Robert C. Gottlieb, said this week he didn't know whether Zazi told prosecutors anything about his client but Zazi's decision to plead guilty "obviously affects the overall prosecution.

Ahmedzay has pleaded not guilty to charges that he lied to the FBI during the probe about places he visited during the 2008 trip.

Zazi's uncle, father and a Queens imam face lesser charges in the case.

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Associated Press writer Pete Yost in Washington contributed to this report.

(This version CORRECTS that Zazi was arrested in September 2009.)