“It is very good that the defence is quick to react on these occasions. It's a sign of increased Russian exercise activity. We have been seeing this for some time, it's a Russian build-up of its military capabilities,” Löfven told reporters as he was heading to Friday's EU summit in Latvia.
The Russian planes were spotted approaching Sweden at lunchtime on Thursday, but did not quite enter Swedish airspace, according to the country's outgoing Supreme Commander Sverker Göranson.
“[They] went out over the Gulf of Finland and then went southwards above the southern tip of Öland,” he told public broadcaster Sveriges Radio on Thursday afternoon.
He added that the aircraft “flew provocatively close” both to Sweden's national borders as well as airspace used by other countries sending aircraft across the Baltic Sea.
The Russian planes were reported to be two Tupolev Tu-22M aircraft, which can carry atomic weapons as well as conventional bombs, but are also used for surveillance.
The incident took place just days before international military air exercise Arctic Challenge 2015 kicks off in the north of the country. Sweden is set to take part alongside eight countries, including Nato member states Germany and the US. The Nordic country is also to set to take part in Nato-led Baltops in the Baltic Sea region at the beginning of June.
“It is important to point out that [Arctic Challenge] is an exercise that demonstrates Sweden's presence in various contexts. We are flexible and that is very good. We need to increase our own military capability and these various collaborations improves that capability. That is why we are taking part, quite simply,” said Löfven, whose Social Democrat-Green coalition opposes full Nato membership.
Sweden's Security Service Säpo, has said that the biggest intelligence threat against Sweden in 2014 came from Russia. The Nordic nation has recently increased defence spending, although there has been strong criticism of the Social Democrat-led government's strategy, with many leading defence experts arguing that Sweden would still struggle to defend itself in the event of an attack from Russia.
It is not the first time Russian aircraft have flown close to Sweden and the latest move follows a similar incident in March this year when two jets were spotted in international airspace but heading towards Sweden's east coast.
In September 2014 two SU-24 fighter-bombers allegedly entered Swedish airspace in what the former Foreign Minister Carl Bildt called “the most serious aerial incursion by the Russians” in almost a decade.
The following month a foreign submarine was spotted in Swedish waters, although the Swedish military was unable to determine where it came from.
These recent incidents have increased calls for the traditionally non-aligned Scandinavian country to join Nato. A poll on Wednesday suggested that one in three Swedes favour Nato membership.