Russian bombers “armed with nuclear warheads” reportedly entered EU airspace before being intercepted by fighter jets.
Swedish media reported that four of Vladimir Putin’s jets flew over Baltic towards the island of Gotland.
TV4, Expressen and Aftonbladet all reported the formation was two Sukhoi Su-24 bombers and two Sukhoi Su-27 fighters.
The bombers were the ones reportedly armed with the nuclear weaponry.
Stockholm’s military has not yet confirmed if the planes carried a nuclear payload.
The warplanes reportedly took off from the Russian airbase in the enclave of Kaliningrad during the incident on March 2.
Sources told TV4 the move is believed to have been a deliberate attempt to intimidate Sweden.
Swedish JAS 39 Gripen jets were sent to intercept the planes - and they were in their airspace for around one minute.
Stockholm confirmed an interception earlier this month, but the reports about the jets being armed with nuclear weaponry only emerged on Wednesday.
A statement from the Swedish armed forces said: “On 2 March, four Russian fighter aircraft violated Swedish airspace. The Swedish air force conducted an operation with JAS 39 Gripen aircraft of the rapid readiness unit, which documented and photographed the incident.
“This demonstrates that our readiness is good. We were on site to secure Sweden’s borders and territorial integrity. We are in full control of the situation”, says Air Force Commander Carl-Johan Edström.
The Swedish airspace was violated by two Russian SU 27 and two Russian SU 24. The incident was brief and took place east of Gotland, out at sea.
“With the current situation as backdrop, we take this incident very seriously. Russia’s conduct is unprofessional and irresponsible.”