Polish border guards said on Thursday they had seen a Russian fishing boat acting suspiciously near a gas pipeline in waters off the town of Wladyslawowo, amid anxiety over possible sabotage operations in the Baltic Sea.
The Baltic Sea is bordered by eight NATO alliance countries that have been redoubling efforts to protect underwater cables and pipelines after a spate of suspected sabotage incidents, some of which the West has blamed on Moscow.
Russia denies involvement.
"On October 1, a Russian fishing boat was spotted by the Border Guard reducing speed while performing suspicious manoeuvres in close proximity to a submarine pipeline belonging to Petrobaltic," the Border Guard said in a statement, referring to the company that works in the area.
"This incident occurred 18 nautical miles (33 kilometres) north of Wladyslawowo. After receiving a radio alert, the skipper sailed away from the critical infrastructure zone."
The Russian embassy in Warsaw did not immediately respond to an emailed request for comment.
Interior Ministry spokesperson Karolina Galecka told reporters that the vessel had been around 300 metres from the pipeline.
Earlier on Thursday, Prime Minister Donald Tusk mentioned an incident near Szczecin port - some 300 kilometres southwest of Wladyslawowo - during a European summit in Copenhagen, without giving further details.
He said there were Russian provocations in the Baltic "almost every day".
Tomasz Siemoniak, minister responsible for special services, said the incident that Tusk had referred to was separate from the one near Wladyslawowo.
(Reporting by Marek Strzelecki, Pawel Florkiewicz, Barbara Erling, Alan Charlish)
