The attackers broke into a building in the Afghan capital following an explosion, according to a security official.
One of them was subsequently killed by guards while another used hand grenades to fend off security forces.
The station’s official Twitter account said staff members reported several casualties, and staffers reached by phone said between two and five people had been killed in the attack.
Kabul police spokesman Basir Mujahid said casualties were feared but the number was still unclear.
More than 100 employees are still believed to be inside the building.
The TV station, Shamshad TV, stopped normal programming and instead transmitted a still image as the attack took place.
The identity or motive of the attackers remains unclear but Taliban insurgents immediately denied any involvement.
Shamshad TV reporter Faisal Zaland, who managed to escape through a back door, said: “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.”
He added: “Many of my colleagues are still in the building.”