BOSTON - Lying grievously wounded in a hospital bed, the surviving suspect in the Boston Marathon bombings admitted on Sunday to playing a role in the attacks, said law enforcement officials, and on Monday he was charged with using a weapon of mass destruction that resulted in three deaths and more than 170 injuries.

Uttering the word "no" once, but mostly nodding in understanding, the suspect, Dzhokhar Tsarnaev, 19, was charged in a brief but dramatic bedside scene in the intensive care ward of Beth Israel Deaconess Medical Center, where he is recovering from multiple gunshot wounds suffered during his capture last week.

Tsarnaev made his admission on Sunday morning to specially trained FBI agents who had been waiting outside his hospital room for him to regain consciousness. After he woke up, they questioned him, invoking a special Justice Department public safety exception that allowed them to interrogate him without telling him he had the right to remain silent.

In the course of questioning him about whether he knew of any other active plots or threats to public safety, he admitted that he had been involved in laying the bombs that killed three people at the finish line of the Boston Marathon.

He said that he knew of no other plots and that he and his brother had acted alone, and he said he knew of no more bombs that had not been detonated.

At the legal hearing Monday, he shook his head in response to most questions. The brief bedside session began when Magistrate Judge Marianne B. Bowler asked a doctor whether Tsarnaev was alert, according to a transcript of the proceeding.

"You can rouse him," the judge told the doctor.

"How are you feeling?" asked the doctor, identified in the transcript only as Dr. Odom. "Are you able to answer some questions?" He nodded.

Bowler then read Tsarnaev his rights. Bowler asked if he understood his right to remain silent, to which he nodded affirmatively, according to the transcript.

The only word Tsarnaev uttered apparently was "No," after he was asked if he could afford a lawyer.

Tsarnaev faces the death penalty or life behind bars. The White House said that Tsarnaev would not be tried as an enemy combatant. "We will prosecute this terrorist through our civilian system of justice," said Jay Carney, the White House press secretary.