The brothers accused of staging the Boston Marathon bombings planned to detonate more explosives in Times Square as they were being hunted by police, New York City officials said Thursday.
New York police chief Ray Kelly said the pair intended to use a pressure-cooker bomb -- similar to the two that erupted at the marathon -- as well as five pipe bombs and improvised grenades they still had on hand as they drove around in a hijacked black Mercedes.
Dzhokhar Tsarnaev confessed the plan to Federal Bureau of Investigation agents in his hospital bed, Mayor Michael 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 reporters.
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, according to Kelly.
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.
But the Republican chairman of the House Intelligence Committee disputed that claim, saying it was more likely the Tsarnaev brothers were planning another attack in Boston instead.
"It's not clear to me that they were actually going to set those devices off, even though they had them with them," Representative Mike Rogers told CNN.
"It's more plausible to me (that) they were going to do another event in the Boston area, and they were hiding out in New York City, (that) was their plan."
Rogers said that ever since the younger Tsarnaev, who is recovering from a bullet wound to his throat, was read his Miranda rights to consult a lawyer and to remain silent, he "has not continued to cooperate with the authorities."
And there are still other "persons of interest" who have yet to be interrogated in the case, Rogers added.
Kelly revealed on Wednesday that Dzhokhar Tsarnaev had told investigators that the pair planned to go to New York "to party."
However, "a subsequent questioning of Dzhokhar revealed that he and his brother decided spontaneously on Times Square as a target," Kelly said at the joint news conference with Bloomberg.
New York police have bolstered security in Times Square since a foiled 2010 plot to set off a car bomb.
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 unleashed a manhunt involving thousands of police.
Dzhokhar Tsarnaev has been charged with using a weapon of mass destruction and could face the death penalty if convicted in US federal court.
The new revelations emerged after the mother of the two men, Zubeidat Tsarnaeva, accused US authorities of needlessly killing her son.
She tearfully expressed regret over the family's move to the United States in 2002, waving her hands and banging the table with emotion.
Tamerlan was "killed, cruelly killed. I want to scream to the whole world, what did you do? He was alive!" Tsarnaeva, wearing a headscarf, said in Makhachkala, the main city in the Russian region of Dagestan.
"I know one thing, that my children did not do this," she added, reaffirming her belief that her sons were innocent of the Boston bombings.
US authorities have said that the older Tsarnaev was killed in a shootout with police.
Tsarnaeva and her estranged husband Anzor Tsarnaev met US investigators in Dagestan this week in a visit organized by the US embassy and the Russian authorities.
The father said he planned to leave for the United States on Friday.
There have been mounting questions in the United States about whether the US authorities missed crucial signals, about Tamerlan in particular, that should have raised suspicions about the brothers before the bombings.