UPDATE 5:07 pm IST: Pakistan Taliban spokesman Muhammad Khorasani has denied that the group was behind Wednesday's terror attack, Reuters reported.
Earlier, Tehreek-e-Taliban commander Umar Mansoor had told AFP that four of their suicide attackers carried out the attack on the Bacha Khan University .
AFP later reported that the Pakistan Taliban leaders had called the attack "unIslamic".
UPDATE 4:25 pm IST: Some reports say that the Taliban has denied responsibility for the Bacha Khan University attack. According to BBC, there are conflicting reports on which group perpetrated the attack.
The Tehreek-e-Taliban (TTP), the Pakistani wing of the Taliban group, launched a deadly attack on the Bacha Khan University in Pakistan's Charsadda district on Wednesday, leaving at least 21 people dead.
Four terrorists stormed the university campus as about 3,000 students and staff were said to be present inside, and opened gunfire. Several explosions were also reportedly heard.
The Pakistan army launched an anti-terror operation at the university, killing the four terrorists.
A professor and several students were said to be among the dead. The death toll is expected to rise, as eyewitnesses reported seeing scores of bodies.
The attack, that took place about 40 kilometres from Peshawar, came just over a year after the Pakistani Taliban attacked the Army Public School in Peshawar and gunned down 134 students.
"Our four suicide attackers carried out the attack on Bacha Khan University today," TTP commander Umar Mansoor told AFP.
Pakistan Prime Minister Nawaz Sharif condemned the Bacha Khan University attack and vowed to continue the fight against terrorism in the country.
Updates so far:
UPDATE 1:20 pm IST: 21 people have been killed in the attack on the Bacha Khan University, paksiatni media reported.
UPDATE 12:50 pm IST: The death toll has risen to 20, according to Khyber Paktunkhwa health minister Shaukat Ali Yousafzai, The Guardian reported.
According to AFP, the military operation inside the campus has ended. The Pakistan Army spokesman had tweeted that there was no gunfire heard for some time.
UPDATE 12:27 pm IST: Four terrorists have been killed so far as army operations continue at the Bacha Khan University, army spokesperson Asim Bajwa said on Twitter. Seven people have been killed, as per latest updates.
UPDATE: 12:09 pm IST: The Tehreek-e-Taliban Pakistan (TTP) have reportedly claimed the attack on the Pakistan university.
The group was also behind the Peshawar school attack in December 2014.
UPDATE 12:06 pm IST: Pakistan Prime Minister Nawaz Sharif condemned the terror attack on Bacha Khan University in a statement released on his official website.
"Those who kill innocent students and civilians have no religion. We are determined and resolved in our commitment to wipe out the menace of terrorism from our homeland," Sharif said.
UPDATE 11:58 am IST: At least three people have been confirmed dead, including a professor and two students, Pakistani media reported.
UPDATE 11:55 am IST: The terrorists have been contained in two blocks within the Bacha Khan University, the army spokesperson said on Twitter.
UPDATE 11 46 am IST: Reports of several casualties are emerging. Dawn News reported at least 15 are feared dead. Two attackers have also been killed.
UPDATE 11:41 am IST: A professor at the Bacha Khan University has been killed in the terror attack, as per reports.
UPDATE 11 37 am IST: The Pakistani Army has begun air surveillance, spokesperson Asim Bajwa said on Twitter.
UPDATE 11:27 am IST: A rescue official told DawnNews that the attackers shot about 60 students 'in the head'.
UPDATE 11:18 am IST: The Pakistan Army's quick response team has entered the Bacha Khan Univeristy campus, as per reports.
UPDATE 10:59 am IST: Two univeristy guards have been injured in the attack, reports said.
UPDATE 10:47 am IST: Two blasts were heard from the university attacked by terrorists on Wednesday, Reuters cited police officials as saying.
UPDATE 10:39 am IST: At least five injured people have been brought out from the university, according to Geo News.
Three armed men entered the Bacha Khan University in Charsadda, located 40 kilometres from Peshawar in Pakistan, and opened gunfire on Wednesday, Pakistani media reported.
There are said to be as many as 3,000 students present inside the university campus, according to The Express Tribune.
Security forces have reached the university where the shooting was reported.
Dawn cited eyewitnesses hearing a blast on the campus.
On Tuesday, a suicide bombing in Peshawar killed at least ten security personnel.
In December 2014, Taliban terrorists stormed an army public school in Peshawar and gunned down over 130 students.