German Chancellor Angela Merkel has accused Russia of risking a further escalation of the conflict in eastern Ukraine by sending an aid convoy into the region without Kiev's permission.

Merkel's office says she called Putin on Friday afternoon to express her "deep concern" about the fact that the convoy had crossed the Russian-Ukrainian border. She also spoke to Ukraine's President Petro Poroshenko about the incident, praising his government's cool-headed reaction.

Merkel says despite Russia's actions, everything should be done to ensure the convoy reaches people in need and the same should be true for a Ukrainian aid convoy that is being blocked by the pro-Russian separatists.

Merkel is traveling to Kiev on Saturday for talks with Ukrainian leaders.