A statement from the Kremlin said Putin delivered the warning in a telephone call with German Chancellor Angela Merkel .
Both leaders emphasized the importance of the plan talks about Ukraine in Geneva on Thursday ( 19 / 04 ) between Russia , Ukraine , United States and the European Union .
A spokesman for U.S. President Barack Obama says the Ukrainian authorities have a responsibility to enforce the law and maintain order throughout Ukraine .
The pro - Russian
Meanwhile , the President of Ukraine Olexander Turchynov said Ukrainian troops have regained control of a military airfield in Kramatorsk in eastern Ukraine , after the fight against the armed group of pro - Russian .
The base is located south of Sloviansk which is one of 10 cities in eastern Ukraine where the government buildings occupied by the pro - Russian .
(see also: harga burung kenari )
About 100 people are believed to be pro - Russian activists were outside the air base .