The call for the $61-million penalty against Dan-Bunkering comes during the company’s trial for the sale of around 172,000 tonnes of jet fuel to Russian firms in 33 transactions between 2015 and 2017.

That fuel was delivered to Syria where it was used in Russian air force planes fighting in the country’s civil war.

“The seriousness of the violation is clear from the fact that the fuel filled the tanks of Russian fighters, which bombed the opposition against (Syrian President Bashar) al-Assad in his name,” prosecutor Anders Rechendorff told the court in Odense.

Keld Demant, the chief executive of Dan-Bunkering’s parent company Bunker Holding, is the target of prosecutor’s demand for a jail term.

Both companies and the boss have pleaded not guilty, saying they had no control over what their customers — themselves not under sanctions — did with the fuel.

But Rechendorff said Demant had not taken due care when reading information about dealing with Russian firms in 2016.

“Even negligence can be grounds for a conviction, and the accused should have examined what was going on much more thoroughly,” he said.

The 647 million kroner (87 million euros) brought in by the fuel sales amounted to around two percent of the company’s revenue in 2015-17.

EU sanctions in force since 2011 against the Syrian regime include a fuel embargo and the freezing of the Damascus central bank’s assets held in the EU.