Pakistan scientist Abdul Qadeer Khan on Wednesday enjoyed his first social outing in more than four years after being detained for leaking nuclear secrets, an official said.

He was taken to the Academy of Sciences from his guarded house in the capital Islamabad to meet old friends for just half an hour, the official who could not be identified told AFP.

"This visit does not mean that restrictions imposed on Dr Khan are lifted," the official said.

Khan fell from grace in February 2004 when he publicly confessed to passing nuclear secrets to other states that authorities later identified as Libya, Iran and North Korea.

He remains a hero to many Pakistanis for transforming the country into the Islamic world's first nuclear power. Pakistan carried out nuclear tests in 1998 in response to detonations by neighbouring India.

Khan was pardoned by President Pervez Musharraf after his confession but has remained in detention at his residence in an upmarket Islamabad neighbourhood.

"I was happy to meet old friends," Khan told AFP by telephone, without giving further details.

Last month he told AFP that he took the blame for passing atomic secrets to Iran, North Korea and Libya in order to "save his country."

Musharraf has repeatedly denied any state involvement in Khan's activities but has rejected international requests to quiz the scientist.