The National newspaper cited an anonymous law enforcement source as saying that al-Haq, a leading al-Qaeda fugitive from Afghanistan and a close associate of late Afghani warlord Maulvi Younas Khalis, was arrested last week in Lahore, the capital of the Punjab province, and is being interrogated by the Pakistani police.
Amin al-Haq, 48, also known under alias Muhammad Amin, was part of the Afghan delegation flown to Sudan in 1996 to bring Osama bin Laden to Afghanistan. He is believed to be an active member of the Hizbe Islami Afghanistan party, which joined the Taliban movement in 1996.
Pakistani authorities have not yet confirmed the arrest.
Meanwhile, Pakistani television reported Monday that suspected Islamic militants killed eight tribal leaders involved in negotiating a ceasefire agreement between the authorities and rebels in the country's northwest.
Local television cited an unidentified law enforcement source as saying that the tribal leaders from the so-called Peace Jirga (Council) were killed in separate attacks late Sunday and early Monday in South Waziristan, a mountainous region bordering Afghanistan.
The region is characterized by a volatile political situation and the presence of various Islamist groups, which are often referred to as Pakistani Taliban fighters.