The scientist, who defected with the list of Indian targets to be hit, has told Sunday Observer that technicians had been asked to prepare the ground for a possible "first use" nuclear strike. They were told to provide data for the explosive yields and weaponisation necessary to attack a variety of Indian targets.

Sunday Observer said the senior scientist had fled with four colleagues to western countries earlier this month in protest against definitive indications that Pakistan planned a "first use policy".

The newspaper claimed a first strike by Pakistan even with low yield weapons could lead to an all-out war with India with hundreds of thousands of deaths.The Pakistani nuclear physicist - an expert in warhead technology and one of the 2,000 scientistswho have been working in great secrecy for the past decade - has asked for political asylum, claiming he was present at meetings when the nuclear targets in India were being discussed.

He said after India's nuclear tests and in the run up to Pakistan's six nuclear blasts two weeks later, he had been asked to provide data for explosive yields required to attack a list of targets and terrains.

Sunday Observer said disclosure that Pakistan was considering "first use" of nuclear weapons has added a "frightening new dimension" to the nuclear stand-off in the Indian sub-continent in the context of Pakistan foreign minister Gohar Ayub Khan's repeated provocative statements that long running dispute over Kashmir could force Pakistan at any time.

Paul Beaver of the Jane's Defence Weekly who broke the scientists' defection story said that the Pakistani weapons expert had escaped after Pakistan's Inter-Services Intelligence made attempts to stop him from fleeing.

"These scientists and technicians have turned upin countries they escaped to with nothing but clothes on their back," Observer quoted an associate of one of the defectors as saying.

"They are still scared. Their families are still in Pakistan and they believe Pakistan intelligence officials are looking for them," the associate said.

The newspaper said the most senior scientist of the group had said his wife had since been arrested in retaliation and to force his return to Pakistan.The defecting scientists, it said, were adamant that they were not being unpatriotic, but were deeply concerned about discussions over targeting of Indian civilian and military centres.

Though it was not immediately known to which countries the scientists had defected, Paul Beaver of the Jane's Defence Weekly which is running the story in its upcoming issue, when asked whether they had sought asylum in the United Kingdom said "may be".

In the run-up to it's own nuclear tests at Chagai in Baluchistan last month, Pakistan had alleged that India with the help of Israel hadintended to send aircraft to destroy its nuclear facilities and test sites. At the height of the nuclear crisis, prime minister Nawaz Sharif had at midnight called up US president Bill Clinton and UK prime minister Tony Blair expressing his fears in this regard.

Pakistani officials, according to Observer, had last night denied that there had been any defections. "All our scientists are here and we never intend to make first use of nuclear weapons," a senior Pakistani official was quoted by the newspaper as saying. It, however, said other senior officials had shown marked embarrassment over approaches concerning missing scientists and refused to answer questions on their whereabouts.