New York's Times Square
New York's Times SquareAFP photo

The brothers accused of staging the Boston Marathon bombings planned a new attack in Times Square as they were being hunted by police, New York Mayor Michael Bloomberg said Thursday.

Dzhokhar Tsarnaev confessed the plan to Federal Bureau of Investigation (FBI) agents in his hospital bed, Bloomberg said, calling it a "horrific reminder that we remain targets for terrorists.”

"Last night we were informed by the FBI that the surviving attacker revealed that New York City was next on their list of targets," Bloomberg told a press conference, according to an AFP report.

The pair -- accused of carrying out the April 15 attacks near the Boston Marathon finish line that killed three people and wounded 264 -- aimed to use their remaining explosives in Times Square, he added.

The 19-year-old and his elder brother Tamerlan Tsarnaev made a "spontaneous" decision to go to New York as they raced around the Boston suburbs in a car with at least six bombs, New York police chief Ray Kelly added.

The pair had a pressure cooker bomb -- similar to the two that erupted at the marathon -- as well as five other pipe bombs and improvised hand grenades as they drove around in the hijacked black Mercedes, according to police.

The night finished with a policeman killed and another gravely wounded. Tamerlan Tsarnaev, 26, was killed in one shootout with police while Dzhokhar, critically wounded, was found Friday hiding in a boat in a suburban backyard.

Kelly revealed on Wednesday that Dzhokhar Tsarnaev had told investigators that the pair planned to go to New York "to party."

"A subsequent questioning of Dzhokhar revealed that he and his brother decided spontaneously on Times Square as a target," Kelly said Thursday at a joint news conference with Bloomberg.

"They would drive to Times Square that same night. They discussed this while driving around in a Mercedes SUV that they had hijacked after they shot and killed an MIT police officer," said Kelly, according to AFP.

The brothers' plan "fell apart when they realized that the vehicle that they hijacked was low on gas and ordered the driver to stop at a nearby gas station. The driver used the opportunity to escape and call the police," Kelly said.

The call by the driver of the hijacked car unleashed a manhunt involving thousands of police.

Dzhokhar Tsarnaev has a bullet wound to his throat but is in "fair" condition and is reported to have communicated with investigators.

He has been charged with using a weapon of mass destruction and could face the death penalty if convicted in U.S. federal court.

The FBI told lawmakers this week that Tamerlan Tsarnaev sent text messages to his mother as early as 2011 suggesting he was willing to die for Islam.

Officials said on Wednesday that both the CIA and the FBI had flagged the deceased bombing suspect over possible terror ties, although no action was deemed necessary at the time.