NEW YORK (AP):

The Boston Marathon bombers were headed for New York to blow up their remaining explosives in Times Square before they were intercepted by police in a blazing gun battle, officials said yesterday.

New York City Police Commissioner Raymond Kelly said Dzhokhar Tsarnaev told interrogators from his hospital bed that he and his older brother had decided spontaneously Thursday night to drive to New York and launch an attack. In their stolen SUV, they had five pipe bombs and a pressure-cooker explosive like the ones that blew up at the marathon, Kelly said.

The plan fell apart when the Tsarnaev brothers got into a shoot-out just outside Boston that left Tamerlan Tsarnaev dead, Kelly said.

"We don't know if we would have been able to stop the terrorists had they arrived here from Boston," Mayor Michael Bloomberg said. "We're just thankful that we didn't have to find out that answer."

Dzhokhar, 19, is charged with carrying out the Boston Marathon bombing that killed three people and wounded more than 260, and he could get the death penalty.

Investigators and lawmakers briefed by the FBI have said that the Tsarnaev brothers, ethnic Chechens from Russia who had lived in the US for about a decade, were motivated by anger over the US wars in Iraq and Afghanistan.

Based on the younger man's interrogation and other evidence, authorities have said it appears so far that the Muslim brothers were radicalised via jihadi material on the Internet instead of by any direct contact with terrorist organisations, but they have said it is still an open question.

Dzhokhar was interrogated in his hospital room over a period of 16 hours without being read his constitutional rights. He immediately stopped talking after a magistrate judge and a representative from the US Attorney's office entered the room and gave him his Miranda warning, according to a US law-enforcement official and others briefed on the interrogation.

Meanwhile, the Tsarnaev brothers' father said yesterday that he is leaving Russia for the US in the next day or two, but their mother said she was still thinking it over.