One of Pakistan's top doctors, freed from detention on Tuesday, says he has been interrogated for the last month by American CIA and FBI agents.

Aamir Aziz, a leading orthopaedic surgeon, says he was grilled about alleged contacts with al-Qaeda, and whether he had helped the group make chemical and nuclear weapons.

The investigations were carried out by the FBI and the CIA

Aamir Aziz

He told reporters he had been held incommunicado in Islamabad since 21 October, but had not been mistreated.

The Pakistani authorities had acknowledged Dr Aziz was being held, but would not say where or by whom, or what he was accused of.

His detention triggered protests by lawyers' and doctors' groups, and a legal challenge by his family.

Tuesday was the deadline by which the authorities had been ordered to produce him before the High Court in Lahore.

'Ridiculous'

Instead, Dr Aziz was brought to his home in Lahore in the middle of the night by security agents.

His eyes are red and swollen due to sleepless nights

Imran Aziz, brother

"I was taken into custody by Pakistani agencies. I was taken to Islamabad where I was lodged in a comfortable house," he told the BBC.

"The investigations were carried out by the FBI and the CIA.

"The allegation was that I had contacts with al-Qaeda and helped them in making chemical, biological, radiological and nuclear weapons.

"It was a most ridulous allegation... By the grace of God, nothing was substantiated."

'I did not treat Bin Laden'

Dr Aziz said he had been treating members of the mujahideen in Afghanistan since 1989, and would continue to do so.

"I treat my patients irrespective of their faith and ethnicity."

But he denied claims he had ever treated al-Qaeda leader Osama Bin Laden or former Taleban head Mullah Omar during trips to Afghanistan.

He had not visited the country since the 11 September attacks last year in the US, he said.

The Pakistani Government abandoned its traditional links with the Taleban after 11 September and pledged to support the US-led war on terror.

US agents are pursuing Taleban and al-Qaeda fugitives in Pakistan.