Moscow on Tuesday demanded answers from Greece and Bulgaria after Sofia banned Russian supply flights to Syria from its airspace and Athens said it had been asked by Washington to do the same.
“If anyone - in this case our Greek and Bulgarian partners - has any doubts, then they, of course, should explain what the problem is,” deputy foreign minister Mikhail Bogdanov told the Interfax news agency.
“If we are talking about them taking some sort of restrictive or prohibitive measures on the Americans' request, then this raises questions about their sovereign right to take decisions about planes from other countries - Russia in particular - crossing their air space,” he said.
“We explain where our planes are flying to, and what their purpose and their cargo is,” he added.
He said that ferrying cargo, which included humanitarian and military aid, through the airspace of a third party - as well as obtaining permission to do so - should be a routine procedure.
“We’ve never had any problems before,” he said.
Washington has expressed concern following reports suggesting Moscow may be boosting military support to Syrian President Bashar al-Assad and had sent a military advance team to the war-torn country.
Earlier on Tuesday, NATO member Bulgaria confirmed it had refused permission late last night for an unspecified number of Russian aircraft to cross its airspace.
Greece said on Monday that Washington had asked it to ban Russian supply flights to Syria from its airspace.
It said it was examining the US request but gave no further details.
Moscow has dismissed US concerns about its alleged Syria buildup, saying its military aid to the Assad regime was nothing out of the ordinary.