STOCKHOLM: Sweden’s armed forces chief warned on Tuesday it could use force to bring to the surface a suspected Russian mini-submarine its navy has been hunting for days.

Battleships, minesweepers, helicopters and more than 200 troops have scoured an area about 30 to 60 kilometres from the Swedish capital since Friday following reports of a “man-made object” in the water.

Supreme Commander General Sverker Goeranson said there was “probable underwater activity” off the coast of Stockholm and he was ready to use “armed force” to bring the mystery vessel to the surface.

Sweden released a hazy photograph of what might be a mini-sub on Sunday.

“The most important value of the operation — regardless of whether we find something — is to send a very clear signal that Sweden and its armed forces are acting and are ready to act when we think this kind of activity is violating our borders,” the general said.

“Our aim now is to force whatever it is up to the surface... with armed force, if necessary,” he added.

Despite widespread speculation that the “activity” is a Russian U-boat — amid unconfirmed reports of intercepted transmissions to the Russian enclave of Kaliningrad on the other side of the Baltic Sea, and the presence of a near stationary Russian oil tanker off Swedish waters since the operation began — authorities in Sweden have not singled out Russia in their comments.

Russia has denied having any submarine in the area, and pointed the finger at the Netherlands, which laughed off the claim, saying its submarine had already docked in the Estonian capital Tallinn after taking part in exercises with the Swedish navy.

“We have not found any vessel. We consider that the reports... confirm something is happening. There is probable underwater activity,” Gen Goeranson told reporters, adding that it was “extremely difficult” to locate submarines.

“We never succeeded in the past — and no one else has either.” Still, he said, the massive military operation — which focused on Tuesday afternoon on the island of Ingaroe, just 30 kilometres from Stockholm — would continue for as long as necessary.

During more than a decade of hunting Russian U-boats in the 1980s and early 90s, Sweden never succeeded in capturing one, except in 1981 when the U137 ran aground several miles from one of Sweden’s largest naval bases.

Published in Dawn, October 22nd, 2014