A fleet of 10 Soviet ships moved into position just beyond Sweden's 12-mile limit Nov. 4 as Russian pressure mounted for the return of Whiskey-class Submarine 137.
The fleet includes two destroyers, two corvettes, and one frigate.
They were being kept under anxious observation by Swedish naval units and air patrols of Viggen jets of the Swedish Air Force.
The show of strength followed a flurry of diplomatic activity as Moscow took a harder line with the submarine affair now into its second week.
Swedish Ambassador Carl de Geer was summoned to the Kremlin twice for talks with Soviet Deputy Foreign Minister Igor Semskov. And in Stockholm Soviet Ambassador Mikhail Jakovlev called at the Swedish Foreign Ministry.
The Swedes would release no details of the contents of these talks. But it is significant that they have bowed to Soviet demands that the submarine's captain, Pyotr Gushin, be interrogated aboard his vessel.
The Swedish government had previously insisted that Gushin be questioned aboard a Swedish warship on his mission deep into Swedish waters.
They saved face by refusing to allow two Soviet diplomats to be present when and if the interrogation is resumed. Military attachcf11e Yuri Prosvirnen and second secretary Boris Grigoriev from the Soviet Embassy in Stockholm had attended Gushin's initial seven-hour grilling Nov. 1 after his submarine was dragged free from the rock on which it was grounded on Oct. 27 in a military restricted area just off Karlskrona, the main southern Swedish naval base.
Gushin is believed to have refused to leave his submarine for continued interrogation on direct orders from his base in Kaliningrad.
Last night the sub was surrounded by Swedish warships and more ships guarded the entrance to the channel.
(The official Soviet news agency Tass broke its nine-day silence and issued a 10-line explanation that the vessel had been on a routine training course and had strayed because of poor visibility, Reuters reported.)