Speaking to Yle on Saturday, President Sauli Niinistö described Belarus's grounding of an internal EU flight last Sunday as a "dramatic, pivotal disruption" of international norms.
Interviewed on the TV1 programme Ykkösaamu, the President said that Belarus's actions were exceptional, as civil transport has previously operated seamlessly even in tense conditions.
According to Niinistö, any repetition of such moves would undermine trust in international cooperation.
Last weekend, Belarus forced a Ryanair flight from Greece to Lithuania to make a sudden landing in Minsk, where Belarusian journalist and activist Roman Protasevich and his female companion were removed from the plane and arrested.
In the past, noted Niinistö, "airspace has been respected even in very tense conditions. In this sense, this is a very dramatic, pivotal intervention in international practice, treaties and customs," he said.
Belarus's internal situation has been worrying for a long time, said the president, who is responsible for overseeing Finnish foreign policy.
"It seems that while the country is drifting more into isolation from Europe, while Russia's influence is growing," Niinistö commented.
EU acted "unusually quickly" against Belarus
Niinistö praised European Union officials for acting "unusually quickly" in regard to Belarus and recognising it as a common security policy issue.
"It is precisely in this type of matter where the EU must be influential [and where] it is better for the EU to act as one than 27 countries separately," he added.
This past week, EU strongly condemned the incident, urged its airlines to avoid Belarus and moved to close its own airspace to Belarusian carriers amid outrage over the interception of the jet and Protasevich's arrest. On Tuesday Finnish national airline Finnair said its planes would stay out of Belarusian airspace until further notice.
The Union plans to impose new sanctions aimed at "inflicting real punishment" on authoritarian President Alexander Lukashenko, likely targeting Belarus's exports and financial sectors, Reuters reports.
The president said it remained to be seen whether Protasevich's case would provoke similar reactions as that of Russian opposition leader Alexei Navalny.
“So far, we have not seen very strong reactions, even in Belarus. When an individual such as Navalny emerges, it's easier for people to get come to grips with the basic problem. Let's see if this leads to similar attitudes," he said.
No plans to mediate
Niinistö said that while he and Finland have often helped to mediate disputes between the EU and its eastern neighbours, he had not been in contact with Lukashenko recently. ** **
The president noted that he has discussed Navalny's case with his Russian counterpart Vladimir Putin several times since the blogger was poisoned last summer and detained in January. Navalny's staff thanked Niinistö for his role in helping to assure Navalny's passage to Germany for medical treatment.
Niinistö has been one of the few EU leaders to maintain a regular dialogue with Putin since Russia's annexation of Ukraine's Crimean Peninsula in 2014.
In April Niinistö held talks with Ukrainian President Volodymyr Zelensky to discuss alleviating tensions on the peninsula and on the Russian border.
Earlier this month, Belarusian opposition leader Svetlana Tikhanovskaya called on Finland to help resolve the country's political crisis.