European Commission spokesperson Carlos Martin said that the worsening of the relations between Greece and Russia is a bilateral matter between the two countries, noting that the Commission is closely monitoring the developments.

Asked on the cancellation of Russian Foreign Minister Sergey Lavrov's scheduled visit to Athens, Martin said that the Commision is available to offer support, reiterated it's strictly a bilateral issue, and declined to make further comments on the matter.

In comments to euractiv.com, Martin warned that generally speaking, "disrespect for other countries’ sovereignty and interference in their domestic affairs is unacceptable".

"The EU has always been clear about this and recognises the challenge, as also evidenced by recent discussions in the European Council," the EU official added.