Prime Minister Kyriakos Mitsotakis' office said two military transport planes were to depart for Poland with "defence equipment" for Ukraine, without adding further details about what they would be carrying.

A separate shipment of humanitarian aid was also to be sent the same day, accompanied by Deputy Defence Minister Nikos Hardalias, the premier's office added.

Also on Sunday, the Greek foreign ministry said it had presented an official complaint to the Russian ambassador over Saturday attacks it said had killed 10 members of the 100,000-strong ethnic Greek community in Ukraine.

On Saturday, Greece accused Russia of "murder" over the deaths in the southeastern Ukrainian villages of Sartana and Buhas.

"The ministry expresses its disgust at these unprovoked military attacks and calls on Russia to respect international humanitarian law and to stop attacks against the civilian population," the foreign ministry said in a statement.

Mitsotakis tweeted on Saturday that "10 innocent civilians of Greek origin" had been killed "by Russian air strikes close to Mariupol".

Six other ethnic Greeks, including a child, were also injured, the foreign ministry said.

The mayor of Sartana has called for an evacuation to the nearby city of Mariupol, it added.

The Russian embassy in Athens has insisted that Moscow is "exclusively" targeting military units and installations in Ukraine.

But Greek foreign ministry spokesman Alexandros Papaioannou on Sunday accused the embassy of lying.

"What the embassy said, I am sorry to say, is fake news. We have proof," Papaioannou told Skai TV. "Orthodox bombs killed Orthodox ethnic Greeks."