Berlin (AFP) - Ukraine's president Monday accused Russia of sending troops and weapons into the ex-Soviet state's conflict-torn east, and warned that a fragile peace deal was not being fully implemented.

"It's terrible that after the Minsk agreement ... we still face serious security problems in the Donbass," Petro Poroshenko said in reference to the pro-Russian separatist region, ahead of talks in Berlin with German Chancellor Angela Merkel.

Kiev and Moscow finalised a ceasefire deal brokered by France and Germany in the Belarus capital of Minsk last February, but sporadic clashes still took place on the frontline.

Poroshenko accused "Russia and its proxies" of failing to observe the ceasefire, and of some 1,200 shellings in January alone.

Observers from the Organisation for Security and Cooperation in Europe (OSCE) are denied access to the border, he said, adding that "this is not surprising as Russia still supplies troops, heavy weapons and ammunition to Donbass over the border and does not want witnesses to these illicit activities."

Merkel also noted that "unfortunately we still, as before, do not have a sustainable ceasefire".

Noting that full implementation of the peace deal was a prerequisite to any easing of Western sanctions against Russia, the German leader said: "We think it is for the good of everybody if Minsk is implemented."

Kiev and the West have accused Russia of supporting the insurgency and sending regular troops across the border, claims that Moscow has repeatedly denied.

Over 9,000 people have been killed and more than 20,000 injured in the conflict in Ukraine since April 2014, according to the United Nations.