A Pro-Russian man prepares molotov cocktails near the town of Slaviansk, eastern Ukraine. Picture: Baz Ratner

Abu Dhabi - UN Secretary General Ban Ki-moon on Monday offered his mediation to help end the escalating crisis in Ukraine.

“I have been discussing this matter will all the parties concerned - Ukranian leaders, leaders of the Russian federation, the European Union, and Americans,” Ban told AFP in Abu Dhabi.

“I am urging these four parties to solve this problem through peaceful means and I'm ready to provide my own role if necessary.”

An agreement to defuse the crisis was reached in Geneva on April 17.

But Russia last week pronounced the accord dead after Kiev stepped up military operations against separatists that Moscow slammed as “war against its own people.”

Ukraine's military battled pro-Russian rebels in a stepped up offensive on Monday, with at least four Ukrainian servicemen killed and 30 wounded battling heavily armed insurgents around the flashpoint eastern town of Slavyansk.

Ban said he was “deeply concerned” by the violence in Ukraine, and called on all parties to implement the Geneva agreement.

“I'm now strongly urging the parties concerned to meet again and look back (at) what has gone wrong, why this agreement has not been implemented, why the parties are now engaging in violence.”

“I am urging again in the strongest terms possible all Ukrainians and partners to address this current issue peacefully before it spins out of control and creates huge consequences beyond anybody's control,” Ban said.

UN spokesman Farhan Haq later said there was “nothing to announce at this stage” about a possible mediation, which would need to be requested by the parties involved.

“Of course the services of the United Nations are always ready if both parties to a conflict or a dispute want those.”

German Foreign Minister Frank-Walter Steinmeier had earlier told German television that he was in talks with the Russians, the United States, the European Union and the Organisation for Security and Cooperation in Europe (OSCE) to hold a second peace conference in Geneva.