This supply "knowingly or unknowingly" helped Islamabad to acquire nuclear capability and was incorporated in its supply framework, it emerged on Monday.

"Japanese companies played a key role in supplying equipment used for Pakistan's nuclear development," Japan's Kyodo News reported, quoting the outcome of its investigations in Islamabad and Tokyo.

Comments by Khan and former employees of the companies reveal in detail for the first time how leading Japanese manufacturers knowingly and unknowingly helped Pakistan acquire nuclear capability and were incorporated into its supply framework.

Investigations revealed that both Khan and the head of the Pakistan Atomic Energy Commission visited Japan at least once in the 1980s to shop for their respective programmes.

Khan, dubbed the "father of Pakistan's nuclear programme," said in a written interview that Khan Research Laboratories acquired a wide range of machines, laboratory equipment and metal products from Japan.

One of the major acquisitions was the import of ring magnets, a key device required to manufacture centrifuges used for enriching uranium, Khan said.

In addition, maraging steel, beryllium thin sheets, beryllium-copper rods and other metal alloys having nuclear applications were also acquired from Japanese firms, according to Khan.

"Japan was also a very, very important country for our imports," he said and identified several Japanese companies from which materials, machines and equipment were acquired, the report said.

According to Khan, a mid-sized Tokyo-based trading company, Western Trading, which went bankrupt in 2004, acted as the point of contact with Khan's side.

Mian Mohammad Farooq, a late Pakistani businessman who headed a Pakistani trading company, brokered several important transactions for Pakistan's nuclear programme with Japan and several other countries.

According to a former employee of Western Trading who spoke on condition of anonymity, the company in the late 1980s exported to Pakistan at least 6,000 ring magnets made by a major Japanese metals producer. Khan also confirmed it.

The former employee said he never heard what the magnets would be used for. "As businessmen of a trading company, the priority is to sell goods," he said, but hastened to add, "of course I always obeyed the export laws."

Khan also said that another key purchase was an electron microscope from Japan Electron Optics Laboratory. An electron microscope is required for testing the strength of the alloys used in the manufacture of centrifuges.

A former JEOL employee of who spoke on condition of anonymity said two such microscopes and an X-ray diffractometer were sold to Khan's organisation for more than 60 million yen. In the interview, he clearly indicated that he was aware of the nuclear nature of the work in which Khan was involved.

"Khan said he wanted to buy a JEOL electron microscope," the former employee said, adding that "the negotiations went smoothly."

In Tokyo, JEOL confirmed in response to a query that it had exported an electron microscope to Khan Research Laboratories in the 1980s but said it was unaware of the work in which the organization was involved.

Kyodo News was also able to confirm that another company, Hitachi Seiki, which went bankrupt in 2002, also supplied equipment such as automatic lathes to Khan through Western Trading.

A Pakistani court earlier this month declared Khan a free man, abolishing his five-year house arrest and other government-imposed restrictions.

Khan, who headed Pakistan's nuclear enrichment programme from 1976 to 2001, confessed in 2004 to transferring nuclear technology to Iran, Libya and North Korea, but he later retracted the confession and claimed he had been framed and made a "scapegoat".

He was pardoned in 2004 by then President Pervez Musharraf in consideration of his services to Pakistan's nuclear program, but remained under virtual house arrest.

According to the court verdict, Khan is now free to talk to the media and express his views in public, free to carry out research and free to move across the country so long as he informs the government of his movements in advance, for security reasons.