Merkel called on Putin to use his influence with the rebels to "avoid a new escalation" of the unrest, her spokesman Steffen Seibert said, a day after heavy rocket fire killed 30 civilians in the eastern port of Mariupol. 

The chancellor also said the rebels, as signatories to the peace agreements signed in Minsk last year, should sit down for talks with representatives from Ukraine, Russia and the Organization for Security and Cooperation in Europe (OSCE).

Merkel also called Ukrainian President Petro Poroshenko to offer her condolences over the Mariupol attacks, which she called "a clear and unjustifiable ceasefire violation", the spokesman added.