Evidence collected so far strongly points to Khan's involvement in the alleged leaks in the late 1980s and early 1990s, they told AFP.

"There is sufficient evidence of linkages between a handful of individuals in Pakistan and the international black market mafia trading in nuclear technology, with Khan being a primary figure in the shadowy business," the government official said, on condition of anonymity.

Pakistan's investigation into the alleged leaks was launched after the UN's International Atomic Energy Agency (IAEA) wrote to the government in November relaying information provided by Tehran about the alleged sales of nuclear know-how.

The letter mentioned names of some Pakistani scientists suspected of selling nuclear know-how for personal profit.

Investigators interrogated and detained nearly a dozen scientists and security officials from Pakistan's main uranium enrichment facility, A.Q. Khan Research Laboratories, named after Khan.

Five have been cleared by investigators, who are still interrogating six others, all with close links to Khan.

Investigators are questioning Khan, 66, but he has not been placed under detention like others.

President Pervez Musharraf said this week that those found guilty of proliferating nuclear technology would be given harsh punishment as "enemies of the state."

Officials admitted Friday there was a division in government circles on how to handle the case against Khan, who is widely revered as a national hero for his contribution to the country's nuclear assets.

"A.Q. Khan is too big to be questioned the way the others are being questioned. The domestic fallout of his questioning might prove unmanageable for the government," the military official, who could not be identified, said.

WAR.WIRE