Dzhokhar Tsarnaev, 19, recovering from serious injuries in a Boston Hospital had told the Federal Bureau of Investigation that he and his older brother Tamerlan, 26, "spontaneously" decided that New York would be next, Mayor Michael Bloomberg said Thursday.
"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 said at a news conference at city hall.
"He and his older brother intended to drive to New York and detonate those explosives in Times Square."
Police Commissioner Raymond Kelly told reporters the suspects had a pressure cooker bomb and five pipe bombs. They had planned to head to New York after hijacking a car and its driver in Boston last Thursday night.
"That plan, however, fell apart when they realised that the vehicle they hijacked was low on gas and ordered the driver to stop at a nearby gas station," Kelly said, adding that the driver escaped and alerted police.
Following 16 hours of interrogation, Tsarnaev stopped responding to investigators' questions after being read his legal rights to remain silent and have a lawyer, according to media reports.
According to the Wall Street Journal, a federal judge decided to advise Dzhokhar Tsarnaev of his Miranda rights, even though investigators apparently still wanted to question him further under a public-safety exception.
The judge's move, made Monday in the hospital where Tsarnaev was recovering, has prompted some Republican lawmakers to press the Justice Department as to why it didn't make a stronger bid to resist the judge's plans, it noted.
"There will be more instances like this, and we will need to have a much better understanding about what is appropriate," House Intelligence Committee Chairman Mike Rogers told the Journal in an interview Thursday.
Meanwhile, the Washington Post reported that nine months before the Boston Marathon bombing, a US counterterrorism task force received a warning that a suspected militant had returned from a lengthy trip to Russia. The reference was evidently to Tamerlan Tsarnaev.
The warning was delivered to a single US Customs and Border Protection official assigned to Boston's Joint Terrorism Task Force, a cell of specialists from federal and local law enforcement agencies, the Post said citing unnamed US officials.
According to a New York Times report, white-suited investigators Thursday combed through the garbage at the Crapo Hill landfill in New Bedford, Massachusetts, near the University of Massachusetts Dartmouth, where Dzhokhar Tsarnaev was a student.
Investigators have been searching for several days for a laptop that they believe belonged to one of the Tsarnev brothers, it said citing a law enforcement official.
A Key lawmaker, meanwhile, has expressed doubts that the suspected marathon bombers acted alone.
"I just find it very hard to believe that two individuals such as this could have obtained the weapons, the explosives, put it all together, arranged this on their own," Republican Peter King, a member of the Select Intelligence and Homeland Security committees told CNN.
"I just think that the investigation was not as thorough as it should have been," he said, saying the questioning of suspect Dzhokhar Tsarnaev prior to reading him his Miranda rights left unanswered several important public safety questions.