A Panamanian-registered bulk carrier sailing from Russia was detained early on Sunday after discharging coal residue into the sea off Sweden’s southern coast, the Swedish coastguard reported.

The captain of the Hui Yuan had admitted the offence and paid a deposit against a fine to be imposed, the coastguard said. The bulk carrier has since been released and is bound for Las Palmas in Spain.

Sweden is among Europe’s most aggressive nations in terms of cracking down on ships linked to Russia, having boarded four ships in just over a month.