Moldova told Russian politicians not to meddle in its internal affairs on Monday after barring a Russian delegation from entering the country ahead of a regional election.
The delegation led by Rustam Minnikhanov, governor of Russia's Tatarstan region, had been due to attend a forum in semi-autonomous Gagauzia region, which holds elections on April 30 to name the head of its government.
Moldova, which applied to join the European Union last year alongside its neighbour Ukraine, has repeatedly accused Russia of trying to destabilise the country, something Moscow denies.
Minnikhanov arrived in an official Tatarstan government plane but was not allowed off the aircraft. Police said in a statement his trip aimed to bolster support for a pro-Russian candidate standing at the elections.
"Supporting a candidate at local elections in Moldova is not a valid reason and the authorities ask Russian bureaucrats to refrain from interfering in the internal affairs of our country," the border guard service said.
Minnikhanov posted a video on social media in which he said he and his delegation had been labelled undesirable, a move he described as regrettable. He said the people of Tatarstan and Gagauzia, both home to Turkic peoples, were "brothers".
Gagauzia is an autonomous region home to a Turkic population that is pro-Russian and Orthodox Christian.
(Reporting by Alexander Tanas; writing by Tom Balmforth; editing by Angus MacSwan)