The carrier has said its crew was instructed to land.
"I acted lawfully to protect our people", Lukashenko said in an address to parliament.
In his first public statement since the Ryanair flight was diverted and opposition journalist and activist Roman Protasevich was arrested on Sunday, Lukashenko dismissed the subsequent worldwide outcry.
The criticism was nothing more than another attempt by his opponents to undermine his rule, he said, accusing them of waging a "modern, hybrid war" against Belarus.
Lukashenko - often dubbed "Europe's last dictator" - is facing some of the strongest global pressure of his 26-year rule of ex-Soviet Belarus.
Putin's spokesman Dmitry Peskov said Wednesday there was no reason to disbelieve Lukashenko's version of events.
ICAO is a United Nations specialized agency, established in 1944 to manage the administration and governance of the Convention on International Civil Aviation (the Chicago Convention).
Lukashenko claims that the flight was diverted because of a bomb threat, saying the threat had originated in Switzerland, allegations that Swiss authorities refute.
All involved countries should take part in the investigation, namely Ireland, where Ryanair is headquartered, Greece, and Lithuania, as respectively the country of origin and destination of the flight, Poland where the aircraft is registered, and obviously, Belarus, whose own report was already transmitted to the ICAO.
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However EU countries are banning Belarusian carriers and the EU has also urged airlines to avoid Belarusian airspace.
Belarus opposition leader Svetlana Tikhanovskaya urged the European Union to be "braver" and impose more sanctions against the Minsk regime. Estonia's foreign minister, Eva-Maria Liimets, appeared to echo those sentiments, telling reporters in Lisbon she hopes sanctions can be focused on "companies which are close to the Belarusian regime".
A nervous-looking Protasevich was last seen in a video released by Belarusian authorities on Monday in which he was seen supposedly admitting to helping to organise mass unrest, a charge that could land him in jail for 15 years. "We believe his life and health could be in danger".
Later on today he protested on the Belarusian border along with dozens of Belarusian and Lithuanian journalists.
Her lawyer said she had been remanded in pre-trial detention for two months and Russian Federation confirmed she was being detained as a criminal suspect.
The statement says the officials "condemn in the strongest terms the unprecedented action by the Belarusian authorities".
Last year's months of protests against Lukashenko, which involved tens of thousands of people, were brutally quashed and thousands were detained. Minsk diverted the flight so that it could arrest opposition activist Roman Protasevich.
After meeting Dutch Prime Minister Mark Rutte in The Hague, Tikhanovskaya said measures being discussed by European Union countries to target Belarusian economic sectors did not go far enough. It called on all ICAO member states, including Belarus and its close ally Russian Federation, to cooperate with the investigation.