The Swedish navy could use force against a foreign vessel believed to be sailing in its waters, a top naval officer said, amid speculation that the ship is a Russian submarine.
In comments made to the BBC on Wednesday, Swedish Real Admiral Anders Grenstad said weapons could be used to raise the mysterious vessel if it refused to surface on its own accord.
The country is entering its seventh day of a search operation prompted by several sightings of the vessel near Stockholm last week.
"If we find the submarine with our own sensors the captain of the ship has the possibility to use weapons to get it to stop whatever it is doing," Grenstad told the BBC.
Moscow has denied rumors that the vessel is a Russian submarine, after distress signals tapped out in Russian were reportedly intercepted last week. Reports of a man in black emerging from the water have also prompted speculation over the involvement of Russia's special forces.
But Grenstad said he had "no clue" who the submarine belonged to.
"Everybody is speculating — that's what you get when you're hunting submarines," Grenstad said.
For some, the naval search has brought back memories of the so-called "submarine hunts" of the 1980s, which saw Sweden aggressively pursue Soviet underwater vessels floating off its coast.
At that time, the Swedish navy was put on heightened alert after a Soviet submarine ran aground off its coast, and it responded to reports of further sightings by laying mines and using depth charges under water.
Amid concerns over the latest sighting, Swedish Prime Minister Stefan Lofven announced Tuesday at a press conference that his government would increase spending on defense in Thursday's budget.