The Islamic State (Isis) terror group has claimed responsibility for an attack at a private TV station in Afghanistan's capital, Kabul.

The group claimed responsibility via its news agency Amaq, adding that it killed at least 20 people, including both guards and staff.

A number of gunmen stormed the building on 7 November following an explosion, witnesses told Reuters.

A staff member who witnessed the attack said gunmen attacked the building after an explosion.

One of them was killed by security guards, while a second one was fought off with hand grenades, an official said.

Officer Jan Agha told AP that one of the attackers was a suicide bomber.

More than 100 employees are thought to be inside the headquarters of Shamshad TV, a Pashto language broadcaster. The TV station stopped programming as it came under attack.

There is no official confirmation on possible casualties.

However, a Twitter handle affiliated with the broadcaster said there were "several casualties".

An employee who managed to escape the attack told the BBC: "Some of my colleagues were killed and injured. I managed to escape."

Reporter Faisal Zaland, who escaped through a back door, told AFP: "I saw three attackers on security cameras entering the TV station building. They first shot the guard and then entered the building. They started throwing grenades and firing."

Kabul has often been targeted by both the Taliban and Isis terror groups in recent months.

Last year, seven journalists working for a private TV station were killed in a car bombing claimed by the Taliban.

Shamshad TV Afghanistan Kabul
Afghan policemen keep watch at the site of an attack at a private television station in Kabul, Afghanistan, November 7, 2017. REUTERS/Omar Sobhani