Prime Minister Gordon Brown on Monday declined to confirm or deny reports about a suspected plot by Al-Qaeda-linked terrorists in Pakistan to hijack an Indian plane and “crash” it into a British city saying the government did not discuss intelligence matters.

“Nobody is going to confirm [this],” he said.

But Mr. Brown played down speculation that the decision, at the weekend, to raise the terror threat level to “severe” was linked to any specific threat. He clarified that while the “severe” alert level implied that an attack was “highly likely” it did not mean that it was “imminent”.

Mr. Brown, who was speaking to reporters at his monthly Downing Street press conference, pointed out that a “number of factors” were taken into account while deciding to raise the threat level. Such a decision was never based on “just one” factor, he said.

He was reacting to a front page report in The Sunday Times that the weekend’s terror alert was prompted by warning from Indian authorities that Al-Qaeda militants planned to hijack an Air India or Indian Airlines plane from either Delhi or Mumbai and use it to attack Britain.

The paper claimed that MI5 was told about the alleged plot by India early last week following the interrogation of Amjad Khwaja, a suspected militant, arrested recently.

It said the warning from the Indian Intelligence Bureau was contained in a “detailed threat assessment” sent to MI5.

Mr. Brown recalled his recent statement in the Commons that Britain faced a “real and serious” threat from international terror groups but said the government was prepared to deal with it and was constantly adapting its response to “changing terrorist techniques.”

“We’re already taking action...We’ve got to show we’re vigilant,” he said.

Last week, he announced a raft of measures to strengthen security at British airports following the Christmas Day failed attempt by a Nigerian youth to blow up a plane over Detroit.