Ukraine's Interior Minister Arsen Avakov says the crisis in eastern Ukraine will be resolved within forty-eight hours; either through negotiations or by force.
Government buildings in the eastern cities of Luhansk, Donetsk and Kharkiv were taken over by pro-Russian activists on Sunday.
The BBC reports some of those who had been inside security service offices in Luhansk since Sunday have left the building.
Mr Avakov said an "anti-terrorist operation" was under way in the three regions and would be concluded within the next two days.
"There are two options," he said on Wednesday, "political settlement through talks or the use of force.
"For those who want dialogue, we propose talks and a political solution. For the minority who want conflict they will get a forceful answer.''
Ukraine said on Tuesday that government building in Kharkiv had been retaken.
Moscow has warned Ukraine that using force to end the protests could lead to civil war.