The probability of a new Russian offensive in eastern Ukraine is very high and may begin after meeting of the European Union on prolonging sanctions against Russia, scheduled to take place on June 29, Ukrainian Prime Minister Arseniy Yatseniuk has said.

"I don’t expect [Putin] will go [on offensive] before June 29, before the EU has to decide on rolling over sanctions. But the chances of a new offensive are very, very high," Yatseniuk said in an interview with The Financial Times.

He said there are thousands of Russian military servicemen in eastern Ukraine.

Yatseniuk added that Ukrainian law enforcement officers had recently captured two Russian intelligence officers who admitted to being Russian military personnel and that they had been ordered to Ukraine.