KABUL, Afghanistan, Aug. 24 (UPI) -- At least 12 people have been killed and several others were injured by gunmen at the American University of Afghanistan on Wednesday, officials said.
According to authorities and news reports, multiple gunmen stormed the Kabul campus late Wednesday. Witnesses heard an explosion and gunfire on the heavily guarded campus.
"We got up, and in the midst of dust ... kept running to the back of the building and climbed the walls and jumped down on the street," one student told NBC News on the way to a hospital after hurting his back and breaking his foot.
"We have been notified of a complex attack on the American University on Darul-Aman Road," the commander of Kabul police's quick reaction force told NBC News.
Those killed include seven students, three policemen and two security guards University spokesman Basir Mujahid said.
Witnesses said the explosion, possibly a suicide bomber, started the attack. Gunfire was still heard about an hour later.
"There might have been hundreds of students and staff of the university when it was attacked," student Makia Muneer said.
CBS News journalist Ahmad Mukhtar said he and some acquaintances escaped but several others, including professors, were trapped inside university buildings. Ejaz Malikzada, a political science graduate of the American University of Afghanistan, said he is receiving calls from friends stuck inside.
"Students need help. They are stuck inside classes," he wrote on Twitter. "So far, AUAF was one of the best universities in Afghanistan, with a spirit of competing with other central Asian universities."
Mujib Mashal, a writer for The New York Times, said on Twitter that police said a car bomb exploded.
It wasn't immediately known who is responsible for the attack.
"An Afghan Special Forces Commander tells me: 'we are moving slowly and carefully. A number of students and faculty inside,'" Bilal Sarwary, an Afghan journalist, wrote on Twitter.
The American University of Afghanistan was the country's first private, not-for-profit university when it was established in 2006. An American faculty member of the college, 27-year-old Lexie Kamerman, was killed in a Taliban attack in 2014. It was also closed earlier this month after an American and Australian professor were kidnapped.
The U.S. Department of State reiterated Wednesday that American citizens are advised against traveling to Afghanistan.
"The security situation in Afghanistan is extremely unstable," it said in a statement.