Pakistan doctors have stepped up protests over the apparent arrest of a leading surgeon, Dr Amir Aziz.

Rallies were held in the three major cities of Islamabad, Karachi and Lahore.

Even if he had treated Osama bin Laden he did so in his capacity as a doctor

Yasmin Rashid of Pakistan Medical Association

Dr Aziz, one of Pakistan's most respected orthopaedic surgeons, is said to have been taken into custody on Monday, apparently on suspicion that he had links with the Taleban.

A joint action committee, representing about a dozen medical trade unions has, threatened to launch a nationwide protest if the government does not release Dr Aziz by Saturday evening (local time).

A resolution tabled by the president of the Punjab University Academic Staff Association, Professor Haris Rashid, called the action against Dr Aziz as "an insult to a noble profession and an attack on Pakistan's sovereignty".

Pakistan's Interior Minister, Moinuddin Haider, has since clarified that the surgeon is being questioned by Pakistani agencies.

Call of duty

"There has been no definite response from the government . So we are giving [it] another 24 hours", said Yasmin Rashid, central leader of Pakistan's Medical Association.

On Thursday, the association had given the government until Friday to release Dr Aziz.

Dr Rashid said the detained surgeon was responding to his call of duty when he went to Afghanistan to treat patients after the US-led military action last year.

His family said Dr Aziz saw the need to rebuild Afghan hospitals

She said: "Even if he had treated Osama bin Laden he did so in his capacity as a doctor. How can you stop a doctor from treating even an enemy's soldiers?"

On Tuesday, colleagues of Dr Aziz said he was detained at a hospital just outside Lahore by Pakistani intelligence officials, who, they alleged, were accompanied by agents from the American FBI.

Dr Aziz visited Afghanistan during the Taleban era - his family said he wanted to rebuild a medical college and had no links with the Taleban themselves.