- Admiral: "At least one" foreign vessel was in Swedish waters
- Helicopters, battleships and minesweepers hunted for the vessel
- Emergency radio call in Russian was picked up by Swedish military, report says
- Russia denies that any vessel was in Swedish waters
Sweden's military feels certain there was an intruder, but it has called off the search for a mystery vessel in waters near Stockholm.
"At least one" foreign vessel was there, Swedish Rear Adm. Anders Grenstad said Friday. "It may have been a small vessel."
Whatever may have been lurking beneath the waves of the archipelago for a week drew threats of martial force from Sweden's military. A spokeswoman warned that the navy was "prepared to use anything necessary" to force the vessel to rise to the surface. The military used battleships, minesweepers and helicopters in the search.
Government officials have not said what they believed they had detected, but Sweden's media reported the military was probably looking for a Russian submarine.
Report: Russian signal
Swedish intelligence had picked up a radio distress call last week -- in Russian -- which set off the defensive reconnaissance, major daily newspaper Svenska Dagbladet reported.
The transmissions were directed at the Russian enclave of Kaliningrad, 330 miles (530 kilometers) south of Stockholm, on the Baltic's southern shore, The Local reported.
Moscow said it had no vessel in Swedish waters and suggested Sweden ask the Netherlands if it was one of theirs stationed nearby.
The Netherlands is a member of a NATO and an ally of Sweden's, which does not belong to the alliance. According to a report, the Dutch said they did not had a sub in Swedish waters.
Russia has recently flexed its muscles at Sweden, which has been cooperating recently more closely with NATO, security expert Gary Schmitt wrote in an analysis for CNN.
Moscow has practiced mock attacks of Stockholm and has flown very close to Swedish planes and ships, he said. It has also encroached upon Swedish airspace.
Tourist sub mix-up
The mystery had unpleasant side effects for tour guide Lasse Schmidt.
He putters around the archipelago with tourists in a small decommissioned military sub originally designed as a target for naval battle exercises.
And the national defense stir had some of his countrymen gunning for him.
They thought his submersible was what the navy detected as a potential intruder. The news of the military's search had Schmidt's business phone ringing, mostly with annoying calls.
"Many people believe we caused this military operation," he said, "and they call to demand that we pay the bill for it."