A deadly ten hour-long terror attack on the American University of Afghanistan in Kabul has ended early Thursday, according to a government’s security officials.

At least 13 people have been killed and 44 wounded including seven students, after the attackers blew up an outer wall before bursting into the university compound around 7pm on Wednesday; casualties may rise.

Elite Afghan forces surrounded the walled compound and eventually worked their way inside, according to a senior interior ministry official.

Sporadic gunfire could be heard through the night and, before dawn, police said the operation had concluded after they killed at least two attackers.

Foreign troops were also involved in the operation to secure the university. A spokesman for the international forces in Kabul said the number of foreign troops was “small”. The troops were “not directly involved or in a combat role, but advising their Afghan counterparts”, Brig Gen Charles Cleveland said.

General Abdul Rahman Rahimi, Kabul’s police chief, said early Thursday that 13 people were killed. Of the 13 killed, he said 7 were students, 4 were police officers and 2 were American University of Afghanistan guards.

Rahimi said 35 students and 9 police officers were injured.

Three attackers were involved in the attack, Rahimi said. The first attacker detonated a suicide car bomb at the entrance the other two managed to enter the campus, he said.

Interior Ministry spokesman Sediq Sediqqi said the attackers were armed with grenades and automatic weapons. The siege of the university lasted almost nine hours, before police killed the two assailants around 3.30 am, he said.

“Most of the dead were killed by gun shots near the windows of their classrooms,” Sediqqi said.

No organization has taken responsibility yet for the attack at the American University of Afghanistan.

Although suspicion falls on the Taliban, the group’s spokesman, Zabihullah Mujahid, would only tell the media that the group is “investigating,” according to The AP.

However, Afghanistan Presidential Palace said the findings of National Directorate of Security (NDS) indicate that the terror attack on American University was organized on the other side of the Durand line, Pakistan.

During an extraordinary session of NDS, President Ghani in a telephone call to Pakistani army chief of staff urged for taking serious measures and arresting the perpetrators of this incident.

Pulitzer Prize-winning photographer Massoud Hossaini tweeted that he was stuck on campus and heard gunshots and explosions, noting “this maybe my last tweets.”

But he escaped. He spoke with the AP about the harrowing experience, saying he was in a classroom with 15 students when he heard an explosion:

” ‘I went to the window to see what was going on, and I saw a person in normal clothes outside. He shot at me and shattered the glass,’ Hossaini said, adding that he fell on the glass and cut his hands.

“The students then barricaded themselves into the classroom, pushing chairs and desks against the door, and staying on the floor.

Hossaini and about nine students managed to escape from the campus through a northern emergency gate.

” ‘As we were running I saw someone lying on the ground face down, they looked like they had been shot in the back,’ he said.”

President Ashraf Ghani’s office said he had visited some of the wounded in hospital on Thursday morning and had also extended condolences to the victims’ families.

President Ashraf Ghani called the assault “a cowardly attempt to hinder progress and development in Afghanistan”.

“Attacking educational institutions and public places and targeting civilians will not only fail to shake our determination, but will further strengthen it to fight and eradicate terror,” he said in a statement.

The U.S. Embassy in Kabul has condemned the “heinous attack” on the American University Of Afghanistan that left 12 people dead, including seven students, three police and two security guards.

U.S. Ambassador P. Michael McKinley called Wednesday’s attack “a cruel and cowardly act.”

“Our thoughts and prayers are with those killed and injured, as well as with the victims’ families, colleagues, and friends,” McKinley said, in a statement. “We remain strongly committed to the people of Afghanistan who are dedicated to establishing lasting peace and security and building the brightest possible future for their children.”

The school says on its website that it “embraces diversity and community” in Afghanistan.

The American University of Afghanistan, which opened 10 years ago, has about 1,700 students.

The attack on AUAF comes two weeks after two teachers working at the university—an American and an Australian—were kidnapped while on their way from their guesthouse to the campus. Their whereabouts are unknown.