"All Sputnik V batches are of the same quality and undergo rigorous quality control at the Gamaleya Institute," said the official Twitter account of the Sputnik V vaccine.
ADVERTISEMENTSlovakia was told to return its Sputnik V coronavirus vaccines "due to multiple contract violations".
It came after Slovakia’s State Institute for Drug Control claimed the vaccines delivered to the country were different to elsewhere.
The institute said it had also not received enough information about Sputnik V to be able to assess its benefits and risks.
The official Twitter account of the Sputnik V vaccine accused Slovakia’s drug regulator of an "act of sabotage" and said it had "launched a disinformation campaign against Sputnik V and plans additional provocation".
It added the vaccine should have been tested in a laboratory that is part of the EU’s Official Medicines Control Laboratory network.
The institute said it "strongly objects to today's misleading claims" from the Sputnik V manufacturer and that the network of EU certified labs is only for vaccines registered in the European Union, which is not the case with Sputnik V.
Sputnik V has not yet been approved for use in the EU, but the body’s regulator, the European Medicines Agency (EMA), started a rolling review of the vaccine last month.
The Russian side called claims the Sputnik V vaccines in Slovakia were different as “fake news.”
"All Sputnik V batches are of the same quality and undergo rigorous quality control at the Gamaleya Institute," it said. "The quality of Sputnik V has been confirmed by regulators in 59 countries."
But the Slovaks said those vaccines seem to "have only the name in common".
Slovakia’s coalition government collapsed last month after Prime Minister Igor Matovic orchestrated a secret deal to buy 2 million Sputnik V vaccines despite disagreements from his coalition partners. Matovic welcomed the first 200,000 Russian vaccines at an airport on March 1.
Matovic, who now serves as the finance minister and deputy prime minister in the new government that was sworn in last week, was in Moscow on Thursday to discuss further vaccine deliveries. The Russians said Kirill Dmitriev, chief executive of the Russian Direct Investment Fund that bankrolled the vaccine and markets it abroad, had "a productive meeting" with Matovic.
But the fund demanded the Slovaks send the Sputnik V to an EU certified lab for testing and asked them to return the vaccines they have received so they "can be used in other countries."
"Congratulations, idiots," Matovic said in a message on Facebook to opponents of the Sputnik deal. He said he was not ready to give it up and was planning to announce his further steps on Friday.
Slovakia's COVID-19 death toll currently stands at 10,243, according to the European Centre for Disease Prevention and Control.
More than 14.5 per cent of its 5.45 million population has received at least one dose of the vaccines, according to Our World in Data.