There have been explosions and gunfire after gunmen attacked the American University of Afghanistan in what local police have described as a "complex attack" with potentially hundreds of people trapped inside the campus.
There are conflicting reports, but US news outlet CBS says that several American professors are inside, as well as possibly hundreds of students. "We have been notified of a complex attack on the American University," a Kabul police official told the network.
"Several gunmen attacked the American University in Kabul and there are reports of gunfire and explosions," the official said. "They are inside the compound and there are foreign professors along with hundreds of students."
A senior interior ministry official said elite Afghan forces had surrounded the university compound and gunfire was ongoing, with Reuters reporting early indications that several gunmen, some wearing suicide vests, were involved.
Ahmad Shaheer, a student at the university, said by telephone that he was trapped inside telling Reuters: "We are stuck inside our classroom and there are bursts of gunfire."
CBS journalist Ahmad Mukhtar tweeted: "I along with my friends escaped and several other of of my friends and professors trapped inside". The attack started at around 7pm local time (4pm BST) after witnesses reported hearing a loud explosion in the surrounding area.
An Associated Press photographer who is inside the university tweeted: "Help we are stuck inside AUAF and shooting flollowed by Explo this maybe my last tweets." (sic)
President of the university told the Associated Press that a militant attack was underway, saying: "We are trying to assess the situation".
The American University of Afghanistan is Afghanistan's only private, not-for-profit, non-partisan and co-educational university. It opened its doors in 2006 with an initial enrollment of 50 students, and today enrolls more than 1,700 full and part-time students.
No group has so far claimed responsibility for the attack, which comes as the Taliban step up their summer fighting season against the Western-backed Kabul government.
On 7 August, two of its professors were kidnapped by men in military uniforms who reportedly abducted them as they traveled between the campus and their home in Kabul.
They have been named as Kevin King, from the US and Timothy Weeks, from Australia and their whereabouts are so far unknown.