Ukraine's President Volodymyr Zelensky held separate telephone calls Thursday with German Chancellor Angela Merkel and European Council head Charles Michel to discuss the security situation on the border with Russia.

Merkel and Zelensky agreed on the cooperation of the international community as well as maintaining sanctions to limit threats posed by Russia, according to a statement from the Presidency of Ukraine.

The parties stressed the importance of the continuation of efforts of the Normandy format, it added.

Earlier Thursday, Merkel warned Russia about its military buildup near the border with Ukraine.

At a news conference with Polish Prime Minister Mateusz Morawiecki, the outgoing chancellor said European Union member states are united and will do everything to prevent new provocations.

In his call with Zelensky, Michel reported on a conversation with Russian President Vladimir Putin on Wednesday.

Michel said that establishing contact between parties with the participation of the EU could help alleviate the crisis, according to a statement by Ukraine.

He wrote on Twitter that he expressed the EU’s full support for Ukraine’s territorial integrity and sovereignty to Zelensky. "Europe’s security is only possible with a secure Ukraine," he added.

Several media outlets reported that the US administration officially warned its European allies that Russia may be planning another invasion of Ukraine.

Kremlin spokesman Dmitry Peskov denied those allegations on Tuesday.

- We have repeatedly stated at various levels that Russia is not going to attack anyone, does not have any aggressive plans - he told reporters at a briefing in Moscow.

Since March 2014, Ukraine has been plagued by conflict in its eastern regions bordering Russia, following Russia’s illegal annexation of Crimea.

Western nations accuse Russia of destabilizing the region by providing military support to separatists.