Protests led by rights groups whose leaders accuse the Pakistani military of being soft on the Islamist militants are common in the volatile north-west of Pakistan.
He was freed on Monday amid a deadly crackdown by security forces that killed about six militants.
“Pakistan remains committed to promoting trade and people-to-people ties with Afghanistan.”
Officials said on Friday that the attack was the deadliest against the army this year.
At least three suspects were arrested overnight in a possible link with the bombing and were being interrogated by intelligence and law-enforcement agencies.
Much of the violence is seen as a reaction by rebels to Beijing’s investment plans in the region to link China’s Xinjiang province with the Arabian Sea in Balochistan.
The U.S. State Department described him as a former journalist and poet who studied at several madrasas in Pakistan.
