STOCKHOLM (AP) — Swedish authorities say they have called off their weeklong search for a suspected submarine in the Stockholm archipelago.

Military authorities said Friday that they have ordered naval and amphibious forces to end their hunt for the submarine, though some ground forces will remain involved.

Sweden's military launched its biggest anti-submarine operation since the twilight of the Soviet Union last Friday after receiving credible reports of foreign underwater activity in the archipelago that extends from the capital, Stockholm, into the Baltic Sea.

Military officials haven't blamed any country for the suspected intrusion, though most Swedish defense analysts say Russia would be a likely culprit.

Sweden built up an anti-submarine force after a Soviet sub with nuclear weapons ran aground off its southern shores in 1981 but started dismantling it as part of deep cuts in defense spending after the Cold War ended. Anti-submarine helicopters were phased out in 2008 and replacements are not expected until 2018.

Apart from cutting defense spending, Sweden has shifted its focus from territorial defense to international peacekeeping operations and abolished conscription. In 2012 Sweden had 20,000 troops on active duty and 200,000 reserves, down from 50,000 active-duty personnel and almost 600,000 reserves in 1999, according to statistics from the Britain-based International Institute for Strategic Studies.