(ANSA) - KIEV - An 'anti-terrorist' operation to confront pro-Russian rebels in the eastern city of Sloviansk has begun after pro-Moscow militants seized control of security forces and police buildings. Interior Minister Arsen Avakov announced the launch of an 'anti-terrorist operation' on his facebook page. He also wrote that a man of security forces died and five injureds. Imprecise the number of victims among pro-Russian rebels.

In a telephone call Us Secretary of State John Kerry urged Russian Foreign Minister Sergei Lavrov to reduce tension in Ukraine to evoid secondary consequences.

United Nations Secretary-General Ban ki-Moon called on for peace and said in a statement he was deeply concerned about the deteriorating situation in eastern Ukraine and "the growing potential for violent clashes".

U.S. Vice President Joe Biden will travel to Kiev on April 22 to meet politician and social leaders. (ANSA).