Sweden exploded three 2,000-pound remote-controlled mines in Hors Bay, 20 miles south of Stockholm, Friday as the search continued for a foreign submarine, officials said yesterday.

Detonating the mines, moored in narrow passages leading into the Baltic to guard the underground Musko Naval Base, was the strongest action yet taken in the nine-day effort to raise the submarine.

Approximately 30 depth charges have been dropped in an attempt to damage the submarine, suspected to be either Soviet or Polish. A second submarine is believed in the area, and a Soviet reconnaissance plane has been monitoring the chase. The Swedes set up a jamming station to prevent communications between the plane and the submarine.

Forty surface ships and 10 helicopters are patrolling the bay, and commandos have been moved to the base to be "ready for any event," said Navy Cmdr. Sven Carlsson.

Use of the underwater mines signaled a harsher attitude toward submarines violating Swedish waters in the area of Musko, an underground network of caves and man-made caves and tunnels built to house submarines and destroyers.

The Norwegian newspaper Bergens Tidende quoted Norwegian government sources as saying the Swedes had identified the intruder as a minisub with a two- or three-man crew. The newspaper reported that sources said the Soviet Union has seven or eight small craft that could be launched from larger submarines for spying missions.

Swedish Navy press spokesmen said they had not heard about the report, but Carlsson said earlier that Swedish military officers believe they are dealing with two submarines, one in the bay and another in the Baltic within Swedish waters.