Marko Djurica/Reuters
A pro-Russia separatist poses for a picture.
The reporter said four separatists in masks, with truncheons and shields, were standing at the entrance to the building controlling access, while more separatists in camouflage fatigues could be seen inside.
About 15 police officers were standing a short distance away but were not trying to resist the separatists.
A crowd of around 400 people surrounded the building and shouted "Russia!" and "Referendum!," a reference to a vote the separatists want to hold on seceding from Ukraine. The protesters later drifted away, but the separatist guards on the doors remained.
One of the masked men at the entrance, asked why the building had been seized, said: "They show lies, they try to influence the people and they broadcast misinformation."
The man, who refused to give his name, said the television station staff were still inside and would shortly be sent home.
Separatists who swear allegiance to the self-proclaimed Donetsk People's Republic already control the regional governor's office and the city hall in Donetsk, the regional capital.
(Reporting by Maria Tsvetkova; Writing by Christian Lowe; Editing by Nigel Stephenson)