MOSCOW/OSLO (Reuters) - Russia on Friday said it had filed a protest to Oslo after Norwegian coastguards detained a Russian trawler near a remote chain of islands in the Arctic earlier this month.

The Norwegian archipelago of Svalbard, about 850 km (500 miles) north of mainland Norway, is seen as a potential flashpoint between Moscow and the West as climate change has opened up the resource-rich region.

Foreign Ministry spokeswoman Maria Zakharova said on Friday Russia was seriously concerned after a Russian fishing vessel named the Borey was detained on April 2, within Norway’s fishery protection zone that Russia considers illegal.

“We believe the practice of detaining foreign vessels by the Norwegian coastguard in the so-called fish protection zone is in line with Norway’s policy of illegally expanding its rights in the archipelago region,” Zakharova was quoted by TASS news agency as saying.

In a statement the Norwegian foreign ministry confirmed the Borey had been arrested by coastguards, saying it was suspected of having contravened Norwegian regulations relating to fishery operations and catches in the fishery protection zone.

“The case was solved under normal procedure at sea and the vessel was released,” the emailed statement added, confirming the ministry had received a verbal protest from Moscow but reiterating the fishery zone had been established legally.

Previous incidents of Russian vessels being detained in the area have been reported in 2003, 2011 and 2016.

Svalbard is regulated by a 1920 treaty which grants Norway sovereignty but allows other signatories, including Russia, residence and commercial rights. A Russian coal mining company has operated there for decades.

Moscow has accused Norway in recent years of flouting the treaty, listing concerns such as Norway’s establishment of the fishery protection zone. Norway has rejected those accusations and said it is fully compliant with the treaty.

The Borey could be seen sailing south of Svalbard earlier this month and last reported its location on April 10 southeast of Bear Island on the edge of Svalbard’s fishing protection zone, shipping data on Refinitiv Eikon showed.