Local media reports have said Farooq Muhammad and Yasin Chohan, senior directors at Pakistan's key uranium enrichment facility Kahuta Research Laboratories (KRL), were taken from their homes earlier this month and have not returned.

But a senior government official told AFP: "The two KRL officials are neither arrested nor detained."

"They are undergoing debriefing sessions conducted by officials from within the sensitive organisations."

The term "sensitive organisations" is used in Pakistan to refer to intelligence agencies.

Local newspapers linked the pair's apparent detention to allegations that Pakistani scientists helped Iran develop its nuclear programs.

The government official, who could not be identified, said there were no specific charges against Muhammad and Chohan.

"This exercise does not stem from any specific charges against these individuals," he said.

Foreign ministry spokesman Masood Khan also denied the men were being interrogated or were in custody, or that any foreigners were involved the matter.

"There is no 'interrogation' going on. The word has implications of 'wrongdoing'. This is prejudgement," Khan told AFP in a written response to e-mailed questions.

"People in debriefing sessions are not held in 'custody'. They are in the presence of those responsible for the conducts of interviews of personnel associated with important organisations."

Khan said the scientists were also undergoing "personnel dependability" assessments.

But he declined to answer whether the men had freedom of movement.

Muhammad's daughter refused to comment on her father's whereabouts when contacted by AFP on Thursday, saying only that her family was fine.

Opposition parties are furious at the scientists' apparent detention and have accused President Pervez Musharraf of trying to appease the United States. The United States has said it would step up its effort to prevent nuclear technology reaching Iran, alleged by Washington to be using an atomic energy program as a cover to develop nuclear weapons.

Pakistan, which declared its nuclear capability in May 1998 with a series of underground nuclear tests, has been accused of sharing nuclear technology with North Korea.

It adamantly denies any kind of nuclear proliferation.

WAR.WIRE