Speaking after reports Khan had suffered a heart attack, Dr. Shafiqur Rehman told AFP he last visited the scientist at his residence in the last week of January when he found him in "poor health."

"He has a history of hypertension and I had been visiting him regularly until I was stopped by the authorities on February 4 after the last visit," the doctor said.

Khan is at the center of a nuclear proliferation scandal and has been blamed by Pakistani authorities for selling nuclear secrets to Iran, North Korea and Libya.

Rehman's father Sajawal Khan, a retired army brigadier, was a civil engineer at the country's uranium enrichment facility Khan Research Laboratories and was detained in January in an investigation into nuclear leaks.

Khan publicly confessed on February 4 to transferring nuclear technology abroad and begged for clemency, after which President Pervez Musharraf gave him a conditional pardon.

Since then authorities have imposed strict restrictions on his movement and tightened security around his residence in Islamabad.

On Monday the foreign ministry said Khan had not been given a blanket pardon and may face further questioning.

Rehman said he was unaware whether Khan had suffered a heart attack, as reported by the leading Pakistani English newspaper Dawn on Monday.

The report, which was promptly denied by the government, quoted sources at the Khan Research Laboratories hospital as saying that a heart specialist and a cardiac machine were secretly sent to Khan's house on February 8.

The report said Khan has "suffered a heart attack" and his condition was "stated to be critical" when he was treated.

Pakistan's foreign ministry said the report was baseless.

"This is fabrication. He is in good health and the report that he suffered heart attack is baseless," foreign ministry spokesman Masood Khan told AFP.

Rehman said a nurse was attending to Khan at his home but no doctor had been sent there.

"Last week I asked the authorities to allow me to check up Khan in the presence of a magistrate but my request was refused," he said.

Officials have said the investigations into the proliferation scandal were continuing with seven other associates of Khan, all under detention.

Pakistan launched an investigation into its nuclear scientists in November after it received a letter from International Atomic Energy Agencyabout information leaks to other countries.

Relatives of the six detained officials demanded the families be allowed to meet the detainees.

"They (detainees) should be given basic right, they should be allowed medical facility and their whereabouts be told to their families so they can meet them," said Hassam ul-Haq, the head of a committee seeking the release of Khan as well as other scientists.

He also said Khan was in "bad health".

He said many people fear that doctor Khan may be killed in the custody. "But let me warn the authorities that if doctor A.Q. Khan dies in the custody it will be considered a cold-blooded murder," he said.

Pakistan has charged the six detainees with "directly or indirectly passing onto foreign countries and individuals secret codes, nuclear materials, substances, machinery, equipment, components, information, documents, sketches, plans, models, articles and notes etc."

Hassam ul-Haq at a news conference denied Khan or any of the scientists were involved in proliferation and accused the United States of orchestrating the scheme to embarrass Pakistan.

He argued that if any proliferation took place it would not have been possible without the connivance of the Pakistani military.

"A general (President Pervez Musharraf) has saved his fellow generals and put the loop on the neck of a civilian (Khan)," Hassam claimed.

WAR.WIRE