Four others were arrested on April 15, Khan said.
Though police have not commented on what those who attacked Khan had apparently taken offence to, he had shared liberal views on the LGBT community, which some say may have prompted the killing.
"Nothing suggests that Mashal, Abdullah, or Zubair committed blasphemy", he said, referring to the three students accused of committing blasphemy by the mob at the university.
Earlier in the day, a large number of protestors took to the streets in the Zaida town, to defend Mashal as they chanted slogans "Be Gunah, Be Gunah (innocent), Mashal Khan Be Gunah".
Iran's President Rouhani to run for second term
President Donald Trump has criticized the nuclear deal and said during his election campaign he would stop Iran's missile program. Rouhani also mentioned the giant joint gas field, the North Field, Iran will be developing with Qatar.
The video of the gruesome violence made via mobile phone cameras shows Khan's disrobed body - covered in blood - being dragged, first in a hallway and then on a road of the campus. Five other students were also injured before the police bring the situation under control.
A professor at Abdul Wali Khan University says a curious student who was killed by a mob after questioning Islam "didn't understand the environment" on campus.
Blasphemy is a hugely sensitive issue in Muslim-majority Pakistan, which introduced the draconian laws in 1985 in a bid to appease rightwing parties.
"While I was in the bathroom of the chairman's office, the angry and furious mob broke the doors and windows and caught me inside the bathroom, where they punched and kicked me".
France's Le Pen hardens her tone in final straight
That worry has been a boon for the far-right party, which has made public safety one of its priorities. Voters in France go to the polls on Sunday in the first round of the presidential elections.
The Center for Research and Security Studies in Pakistan estimates that at least 65 people have been killed over blasphemy allegations since 1990, and dozens more convicted of the crime are on death row.
"Eight students were presented before an anti-terrorism court in Mardan over murder and challenging the writ of the state", public prosecutor Rafiullah Khan said.
In a statement released to the press on Saturday, Prime Minister Nawaz Sharif said he was "shocked and saddened by the senseless display of mob justice that resulted in the murder of a young student, Mashal Khan, at Wali Khan University".
Mardan police chief Mohammad Alam Shinwari denied the allegation that officers did not do enough to save Khan.
Jeremy Corbyn vows to tackle 'rigged system' in battle with establishment
Labour is seeking to focus the election on policy, given Mr Corbyn's dismal personal poll ratings. Corbyn was defiant about the Labour's ability to woo voters up and down the country.
FILE - Students chant slogans while holding banners and posters showing Mumtaz Qadri, the killer of Punjab Governor Salman Taseer, during a rally to protest against any attempts to modify blasphemy laws, in Karachi, Pakistan, Jan. 20, 2011.