European airlines began skirting Belarus on Tuesday at the urging of the European Union, which also imposed new sanctions to punish the ex-Soviet nation’s forced diversion of a passenger jet to arrest an opposition journalist.

In unusually swift action at a summit in Brussels, EU leaders agreed on Monday to ban Belarusian airlines from using the airspace and airports of the 27-nation bloc, imposed sanctions on officials linked to Sunday’s flight diversion, and urged the International Civil Aviation Organisation to start an investigation into the episode some described as state terrorism or piracy.

Belarus has defended its actions and its Transport Ministry said on Tuesday that it has invited representatives of the international aviation organisation and US and EU authorities to investigate the flight’s diversion.

Polish carrier LOT and Baltic airlines have begun bypassing Belarus. Air France, KLM, Finnair, Lufthansa and Austrian Airlines have all said they will also avoid flights over the country. The UK, which is no longer part of the EU, also recommended that carriers do not fly over Belarus, and British Airways flights were avoiding the country.

In a sign that tensions remained high, Nato secretary-general Jens Stoltenberg described the Ryanair flight’s diversion as “dangerous and unacceptable” and welcomed the EU response.

“This is a state hijacking and demonstrates how the regime in Minsk attacks basic democratic rights and cracks down on freedom of expression and independent media,” Mr Stoltenberg said.

On Sunday, Belarusian flight controllers told the crew of a Ryanair jetliner flying from Greece to Lithuania that there was a bomb threat against the plane as it was crossing through Belarus airspace and ordered it to land.

A Belarusian MiG-29 fighter jet was scrambled to escort the plane in a show of force by President Alexander Lukashenko, who has ruled the country with an iron fist for more than a quarter of a century.

Belarus authorities then arrested 26-year-old journalist and activist Roman Protasevich and his Russian girlfriend, Sofia Sapega. Protasevich was later seen in a brief video clip shown on Belarusian state television, speaking quickly and saying that he was giving testimony about organising mass disturbances.

Protasevich, who left Belarus in 2019 and ran a popular messaging app that played a key role in helping organise huge protests against Lukashenko, has been charged in absentia with staging mass riots and fanning social hatred. Those charges carry a prison sentence of up to 15 years.

The Telegram messaging app’s Nexta channel that he co-founded has been labelled as “extremist” by the Belarusian authorities, and some fear Protasevich could face more serious charges, including some that carry the death penalty.

US President Joe Biden said late on Monday that he asked his team to develop appropriate options to hold accountable those responsible, in close coordination with the European Union, other allies and partners, and international organisations.

“This outrageous incident and the video Mr Protasevich appears to have made under duress are shameful assaults on both political dissent and the freedom of the press,” Mr Biden’s statement said.

Belarus has been rocked by months of protests, which were triggered by Lukashenko’s re-election to a sixth term in an August 2020 vote that the opposition rejected as rigged. More than 34,000 people have been arrested in Belarus since then, and thousands beaten.