''Whiskey'' 137, the Soviet submarine that went aground in a top-secret military area of Swedish territorial waters, was armed with nuclear weapons, Swedish Premier Thorbjorn Falldin said Nov. 5.
Falldin said that Swedish experts who boarded the submarine found evidence that its torpedoes were armed with nuclear warheads. However, according to a US Navy source, the main armament of Whiskey subs is the SSN-3 antiship or tactical nuclear missile.
It is now thought in Sweden that the Soviet sub was sent to get information about a new antisubmarine torpedo being tested in the Karlskrona area last week. Instead the submarine ran aground on rocks in a military restricted area.
An official protest had been made to the Soviet ambassador in Stockholm, Mikhail Yakovlev, who had not denied the presence of the nuclear warheads but said that the submarine's armaments had nothing to do with its violation of Swedish territory.
The protest said: ''The Swedish government is compelled to note with dismay and indignation that the grounded submarine probably has one or more nuclear warheads on board.
''The investigations show that it is practically certain that uranium 238 is present on board the submarine aforeships.
''On account of the extreme importance of the matter, the Swedish government has immediately demanded that the Soviet government present a clarification as to whether or not nuclear weapons are present aboard the submarine. The Soviet Union has ignored the request for clarification on this point.''
Despite this latest, sensational development, Falldin said the submarine would be returned to the Soviet Union ''as soon as weather permits.''
Plans to hand the sub over Nov. 5 were abandoned when a new storm hit the Karlskrona Archipelago, where the 25-year-old sub is imprisoned, surrounded by Swedish warships.
Falldin reported that Swedish experts said there was no danger of leakage of radiation from the submarine.
He said the Swedish government believed it likely that the submarine was ''engaged in forbidden activities in Swedish waters but it is difficult to say what these were.''
Russian references to the Baltic as ''a sea of peace'' were no longer valid as a result of the Whiskey 137 affair, said Falldin.
Gen. Lannart Ljung, supreme commander of the Swedish Armed Forces said: ''we have ruled out that there was a navigational fault.''
This was a reference to the explanation Whiskey's captain, Pyotr Gushin, offered for his presence in Swedish waters, still the official Soviet line.
General Ljung said that when weather permitted Whiskey would be towed out to sea where a Soviet fleet of 10 ships is waiting for it, just beyond the Swedish 12-mile limit. He said it would be accompanied by helicopter gunships and torpedo boats.
Asked if the gyrocompass was smashed, General Ljung said: ''just about every piece of equipment aboard was smashed by the time we were allowed on board to carry out our inspection.''
Foreign Minister Ola Ullsten read the full text of Moscow's reply to Swedish allegations that Whiskey was armed with nuclear warheads:
''The Soviet Submarine 137 carries, as do all other naval vessels at sea, the necessary weapons and ammunition. However, this has nothing to do with the circumstances surrounding the unintentional intrusion by the submarine into Sweden's territorial waters.''
Ullsten said he then informed Ambassador Yakovlev: ''As regards our question about the presence of nuclear weapons your answer is that the submarine carries the necessary weapons and ammunition.
''This means, as far as I can see, that you do not deny the presence of nuclear weapons on board the submarine.
''I wish to inform you, Mr. Ambassador, that the Swedish government will meet tomorrow morning at nine o'clock. If by that time we have received no other information than that which you have now given us, the Swedish government reserves the right to take appropriate measures.''