VIENNA: The leaders of Austria, the Czech Republic, Bulgaria, Slovenia and Latvia have written to the European Union calling for a discussion on COVID-19 vaccine distribution within the bloc after Austria complained it was uneven.

Austrian Chancellor Sebastian Kurz said on Friday that vaccine doses were not being spread evenly among member states despite an agreement within the bloc to do so according to population. He blamed separate deals struck between the EU's vaccination steering board and drug companies.

Kurz said on Twitter on Saturday that he and his four counterparts had called for discussions to find "a European solution" in a joint letter. The letter, to European Commission President Ursula von der Leyen and European Council President Charles Michel, was published by Austrian media.

"In recent days ... we have discovered that ... deliveries of vaccine doses by pharma companies to individual EU member states are not being implemented on an equal basis following the pro rata population key," the letter said.

"We therefore call on you, Charles, to hold a discussion on this important matter among leaders as soon as possible."

Malta is on course to have three times more vaccine doses relative to its population by the end of June than Bulgaria, Kurz has said.

The letter did not mention the steering group, which has long been known to be part of a mechanism by which member states share excess doses among themselves. The deputy head of the steering board is Austrian.

Opposition parties have accused Kurz of trying to deflect blame for the slow pace of vaccinations away from himself. The Social Democrats said he was seeking "scapegoats for his failure".

An EU official said Michel had received the letter and a leaders' summit was already planned for March 25 and 26.

"COVID coordination will again be addressed by the 27 members during that meeting," the official said, without specifying whether that included vaccine distribution.

Michel's office declined to comment.