Police re-captured the administrative headquarters of the eastern Ukrainian city of Donetsk and have around 68 pro-Russian protesters in custody who are being questioned over the occupation.

Ukraine put its armed forces on full combat alert and warned Russia that any military intervention in the country would lead to war.

After a more than three-hour meeting with security and defence chiefs, Acting President Oleksander Turchinov said there was no justification for what he called Russian aggression against his country.

Standing beside Turchinov, Prime Minister Arseny Yatseniuk said he had urged Russia to return its troops to base in the Crimea region during a phone call with Prime Minister Dmitry Medvedev and called for talks.