NATO Secretary-General Jens Stoltenberg says he thinks it is likely that Belarusian authorities organized the diversion last week of an Irish airliner to Minsk with ally Russia.
The military alliance leader was speaking to Sky News on May 28 aboard a British aircraft carrier during NATO's largest military exercises of the year.
"We know the very close relationship between Russia and Belarus, and therefore it's hard to believe that the regime in Minsk could do something like this without any kind of coordination with Russia," Stoltenberg said.
Alyaksandr Lukashenka has relied heavily on Moscow's support since a fiercely disputed reelection bid in August 2020 that sparked massive public protests and a fierce crackdown on dissent.
A Ryanair flight was diverted during a flight between Greece and Lithuania on May 23 after Lukashenka ordered a MiG-29 fighter jet to accompany the aircraft because Belarusian authorities said they had received information there was a bomb aboard the plane.
No bomb was found when the aircraft was searched on the ground in Minsk, but Lukashenka critic and journalist Raman Pratasevich and a Russian friend aboard the flight were detained.
The United States and others believe the incident was staged as a "false pretense" to snatch Pratasevich.
Many governments and rights groups have demanded Pratasevich's release, and Belarusian opposition leaders have expressed fears for his life.
Lukashenka met with Russian President Vladimir Putin in Sochi on May 28, where the Russian leader described international reaction to the airliner's diversion as an "outburst of emotions."
Washington has imposed fresh Belarusian sanctions and is coordinating with the European Union and other partners to impose other penalties on Minsk.
Many governments have advised their airlines to avoid Belarusian airspace.
EU foreign-policy chief Josep Borrell warned on May 28 there was a risk of an escalation after Moscow denied access to two European carriers that skirted Belarus en route to Moscow.
Crisis In Belarus
Read our coverage as Belarusians continue to demand the resignation of Alyaksandr Lukashenka amid a brutal crackdown on protesters. The West refuses to recognize him as the country's legitimate leader after an August 9 election considered fraudulent.