Media playback is unsupported on your device Media caption Shaima Khalil: "Today's attack will raise questions about why the militants are still able to strike soft targets"

Vigils have been held in Peshawar and elsewhere in Pakistan for at least 21 people killed in a university attack.

Four suspected attackers also died in Wednesday's assault on Bacha Khan University in Charsadda.

Military spokesman Lt Gen Asim Bajwa told reporters that major breakthroughs had been made in identifying the attackers but did not name them.

One Pakistani Taliban commander said the group carried out the assault, but its main spokesman denied this.

The group killed 130 students at a school in Peshawar in 2014.

Image copyright AP Image caption University students gathered to pray for the victims of Wednesday's attack

Survivor recalls 'horrible and wild attack'

How the attack unfolded

Why can't Pakistan stop the militants?

Media playback is unsupported on your device Media caption Footage shows the inside of Bacha Khan University after the violence

Early on Wednesday, gunmen entered Bacha Khan University in Charsadda, 50km (30 miles) from Peshawar, and opened fire on students and faculty as they gathered for a poetry event.

Those killed were a professor, two gardeners, one caretaker and 17 students, according to Pir Shahab, superintendent of investigations, who spoke to AFP news agency. Most of the victims were shot dead at a hostel for male students.

The death toll rose to 21 after two of the injured died in hospital, police said on Thursday. Officials say seven other survivors are in a stable condition, AFP reports.

The attack sparked widespread outrage in the country and candlelight vigils were held for the victims in the south-western city of Quetta. Dozens of people protested in Karachi.

Authorities say they have gathered information from the mobile phones of the attackers about where they came from and who sent them.

"The terrorists were continuously conversing on their mobile phones, two of which we have recovered," Lt Gen Bajwa said.

But he said the information was "sensitive" and would be shared with the public later, according to Dawn newspaper.

BBC Urdu's Asad Ali Chaudry says there is a symbolic value attached to Bacha Khan University, as it is named after a Pashtun nationalist leader who believed in non-violent struggle.

The title of Wednesday's poetry programme in his honour was "peace", he adds.

Just days ago, some schools in Peshawar were closed by the authorities amid reports that militants were planning an attack.

Deadly recent attacks in Pakistan

Image copyright AP Image caption Shia Muslims were attacked in Karachi in May