Pakistan's army says it is questioning four more officers about suspected ties to a banned Islamic extremist group.

Army spokesman Major General Athar Abbas said Wednesday that the four army majors are being questioned for suspected links with Hizb-ut-Tahrir, but have not been detained.

The interrogation of the officers comes a day after the army said it detained Brigadier General Ali Khan over his links to the extremist group.

Hizb-ut-Tahrir is an international Islamist organization that calls for a return to a pan-Islamic Caliphate under Islamic law. Although the group does not advocate violence, it is believed to have links to militant groups.

Many critics in Pakistan and around the world say the Pakistani military is deeply infiltrated by extremist groups, making suspect its loyalty in the international effort against terrorism.

The discovery of Osama bin Laden in Pakistan has raised questions as to whether members of Pakistan's military or intelligence knew the al-Qaida leader was hiding out not far from the capital, Islamabad.

Pakistan has rejected such allegations and insists it is doing everything it can to combat militancy.

Bin Laden was killed in a May 2 raid by U.S. special forces in the Pakistani city of Abbottabad.