File photo: Maria Tsvetkova.

Berlin - Russia's actions inside Ukraine “add up to a military intervention,” German Chancellor Angela Merkel's spokesman said Friday, ahead of an EU summit that will consider fresh sanctions against Moscow.

“Russia is strongly urged to refrain from all actions that mean a further escalation,” said the spokesman, Steffen Seibert, pointing to a growing number of sightings of Russian fighters and arms inside Ukraine.

“Regarding the reports of repeated violations of the Ukrainian border, which add up to a military intervention, we expect clarification from Russia,” he said. “This is a very serious and unjustifiable development.”

Seibert reiterated Merkel's comments Thursday that Berlin wants “a diplomatic solution” to the crisis but that EU leaders at a Brussels summit Saturday must consider stepped-up sanctions against Russia.

“If there is an escalation, if Russia fails to meet its responsibility Ä to stabilise the situation, ... to use its influence with the separatists, to close the border to Russian military equipment and Russian fighters Ä then Europe will again have to respond,” he told a press conference.

“And that is why the European Council will have to address possible measures.”