The European Union’s air-safety regulator told airlines to avoid flying over Belarus, saying the diversion of a Ryanair Holdings Plc flight on Sunday raised doubts about the Eastern European nation’s respect for international aviation rules.

The safety bulletin issued by the European Union Aviation Safety Agency unifies the region after several of its member states and the U.K. issued similar guidelines. While the advisories aren’t binding, airlines tend to follow them.

Carriers started to avoid Belarus earlier this week, in response to the re-routing of a Ryanair flight to Minsk, where authorities detained a dissident journalist. Governments from Europe to the U.S. have rejected the contention of Belarusian officials that the detour was necessary because of a bomb threat.

Britain took the further step of banning Belarusian airlines including state carrier Belavia from British airspace.

EASA said the May 23 incident “amounted to an increased safety risk” for the flight and “put into question the ability of Belarus to provide safe air navigation services.” The country’s actions raise “serious doubts on the respect shown by Belarus for international civil aviation rules.”

Operations in airspace controlled by Minsk, the Belarusian capital, should be avoided unless deemed necessary to ensure safe operation in case of unforeseen circumstances, EASA said.