Tensions between Russia and Belarus flared yesterday less than a month ahead of presidential elections in Moscow's western neighbour expected to be swept by strongman president Alexander Lukashenko.
The Kremlin ordered Foreign Minister Sergei Lavrov to avoid all contact with Lukashenko on a visit to Minsk, reports said, an unprecedented gesture to a country that was an unstinting ally for most of the post-Soviet period.
"The meeting was not planned as the head of the Russian foreign ministry had precise instructions from the Russian president to that effect," the RIA Novosti state news agency quoted a Kremlin source as saying.
Relations between Minsk and Moscow have nose-dived in recent months as Lukashenko, famously once slammed by the US as "Europe's last dictator" sought to loosen ties with Russia.
Lavrov, spreaking at a news conference in Minsk, confirmed that a meeting with Lukashenko was not on his schedule.
"When we were agreeing on the visit to Minsk we did not talk about any other events," Lavrov said after regular talks with his Belarussian counterpart Sergei Martynov.
"Decisions were taken that have important practical and not some abstract meaning for the interests of our countries in the sphere of foreign policy co-ordination," he said.
The lack of a meeting with Lukashenko on Lavrov's visit will be seen as a sign the Kremlin has no intention of backing the president even if, as expected, he wins the vote.
Lukashenko traditionally meets with all top Russian dignitaries.
The Interfax news agency, citing a source in Lukashenko's inner circle, said that Medvedev had indeed forbidden his officials to meet with Lukashenko.
"We are aware that Russia has banned contacts between leading Russian ministers and governors and representatives of the Belarussian side," the source was quoted as saying.
Russia's Kommersant daily gave a different version of events, saying that it was Lukashenko who snubbed Lavrov by refusing to meet him on his visit to the Belarussian capital.
The mercurial Lukashenko has in recent years made more positive noises to the West and become increasingly unpredictable towards Russia.
In June, Russia drastically cut gas supplies to Belarus amid a row over payments.
Lukashenko has ruled the state of 10mn that lies between three EU states and Russia since 1994. He has long promoted a folksy image at home and likes to be known as "batka" (dad).
Ten candidates have registered to stand in the polls, scheduled for December 19.
Despite Russia's changing sympathies, observers say a victory for the incumbent president is a foregone conclusion, although Moscow could create difficulties for him in the aftermath of the vote.