Militants attack American University in Kabul

At least one person was killed and 24 injured after militants stormed the American University of Afghanistan in Kabul, trapping students and staff inside amid explosions and heavy gunfire.

Dozens of special forces cordoned off the area after the attack started on Wednesday evening, when the private university is usually packed with students, many of them working professionals doing part-time courses.

"I heard explosions and gunfire is going on close by... our classroom is filled with smoke and dust," said an anxious student.

"We are stuck inside and very afraid," she told AFP by telephone.

Many other trapped students were tweeting desperate messages for help, with some using classroom furniture to barricade the doors.

Among them was Associated Press photojournalist Massoud Hossaini, who was said to be wounded and later managed to escape with some fellow students.

"Many students have been evacuated," said interior ministry spokesman Sediq Sediqqi, adding that there were no immediate reports of any hostages taken by the attackers.

"We are not sure about the number of attackers... but our special forces have started clearance operations."

US military advisers were also assisting Afghan forces to respond to the attack, an American defence official said.

Kabul-based journalist Ahmad Mukhtar, a university student, tweeted that he managed to escape but "several of my friends and professors (are) trapped inside".

Ambulances rushed to the scene as erratic gunshots rang out from inside the campus.

The Italian-run Emergency Hospital in Kabul tweeted that at least five wounded people had been brought to the facility for treatment.

The attack, which underscores the worsening security situation in Afghanistan, comes as Taliban insurgents step up their summer fighting season against the Western-backed Kabul government.

However, no group has so far claimed responsibility for the assault, which comes just weeks after two university professors - an American and an Australian - were kidnapped at gunpoint near the school.