Russia has denied entry to two European airlines because they planned to avoid flying over Belarus to get to Moscow.
Air France and Austrian Airlines have both had to cancel services after their flight plans were rejected by Russia.
EU leaders asked European carriers to avoid Belarusian airspace this week after a Ryanair plane was forced to divert and land in Minsk on Sunday.
Belarusian dissident journalist Roman Protasevich and his girlfriend were then arrested.
The UN’s civil aviation agency has said it will launch a “fact-finding” investigation into Belarus’s actions, and whether there had been any breach of international aviation law.
Russia is a strong ally of Belarus and President Vladimir Putin is set to discuss the unfolding crisis with Belarus’s leader of 26 years, Alexander Lukashenko, in the Russian resort of Sochi on Friday.
The decision to refuse entry to specific flights is the first move from the Kremlin over the diplomatic conflict. Other flights involving German carrier Lufthansa and Polish airline Lot have arrived as scheduled. Russia is yet to comment on the action it is taking.
The European Union and UK have banned Belarusian airlines from flying over their territories, and have said more sanctions are to come, including against Mr Lukashenko and other senior officials. EU foreign policy chief Josep Borrell says there are plans “on the table” to target key economic sectors.
The European airspace ban has forced Belarusian carrier Belavia to cancel 12 of its routes until 30 October, according to Reuters. The routes affected are Amsterdam, Barcelona, Berlin, Brussels, Frankfurt, Hanover, Kaliningrad, Milan, Munich, Rome, Vienna and Warsaw.
Belarus will lose out on millions of dollars a year in over-flight fees as a result of European airlines avoiding Belarusian airspace.
Russia’s move in support of Mr Lukashenko has led to the cancellation of at least four Air France flights between Paris and Moscow. Some passengers were rebooked on Russian carrier Aeroflot.
Two Austrian Airlines flights have been grounded – one passenger plane travelling from Vienna to Moscow, and a cargo plane travelling from Nanjing in China to Vienna.
Austria’s foreign ministry said Russia’s actions were “absolutely incomprehensible”. The French ministry of transport told AFP news agency that “the principle of reciprocity… must be respected”.
Tracking website Flightradar24 showed little activity in the skies over Belarus on Thursday, except for Belarusian and Russian airlines.
On Wednesday, the website showed a Minsk to Barcelona flight, operated by the Belarusian airline Belavia, in a long holding pattern at the border with Poland, which has banned Belarusian flights from its airspace. The plane eventually returned to Minsk. The BBC has contacted Belavia for clarification on why it turned back.
On Sunday, Ryanair Flight 4978 was travelling from Athens to Vilnius in Lithuania, when it was forcibly diverted to Minsk. A fighter jet was scrambled to tail the plane and ensure it changed course.
Aboard was Mr Protasevich, 26, who lives in exile in Lithuania, and his girlfriend Sofia Sapega, 23, an international law student. They were arrested as passengers disembarked.
Mr Protasevich was put on the Belarus terrorist list last year, and faces serious charges.
On Thursday, Mr Protasevich was able to see his lawyer for the first time.
“All is well, he is vigorous, positive and cheerful, there is nothing to worry about,” Inesa Alenskaya was quoted as saying by the Belorusskiye Novosti website, adding she could not give any more information.
Russia’s foreign ministry says Ms Sapega is accused of breaking Belarusian law in August and September of 2020. But it is unclear what these crimes are.
Videos were released showing the pair confessing to crimes, but it is likely they were speaking under duress.
The forced landing of the plane and their arrest caused international outrage.
“It was a serious attack on the rules governing civil aviation… This action also represents a serious attack on media freedom,” a statement by the G7 nations of Canada, France, Germany, Italy, Japan, the UK and the US said.