“This is the most serious security situation in many decades,” Jonas Gahr Støre told a press conference on Monday. “There are no signs that Russia is expanding its war to other countries, but heightened tensions make us more exposed to threats, intelligence operations and influence campaigns.” Gahr Støre said that “there is no reason to believe that Russia will want to invade Norway or any other country immediately.” “We have to be more careful,” he added. “I don’t think ordinary people will notice any change.” Norway will also seek to bring its new fleet of US-made P-8 Poseidon submarine patrol aircraft into service at a faster pace than originally planned, defense chief Gen. Eirik Kristoffersen said. The armed forces would spend less time training and more time on operational tasks, and the home guard, a rapid mobilization force, would play a more active role, Defense Minister Bjorn Arild Gram said. The Air Force had stopped training in the US with its F-35 fighters, preferring to keep them in Norway, Kristoffersen said. “We expect this situation to last for at least a year,” he said. Gahr Støre stressed that nothing had happened in the last few hours to cause the alert to increase, which was “due to developments over time”. Norway has a 198 km (123 mi) border with Russia in the Arctic. Last week, Norwegian authorities arrested a man who they said posed as a Brazilian scholar but was allegedly a Russian intelligence officer suspected of espionage. Norway’s internal intelligence agency PST said his name was Mikhail Mikushin. The suspect was detained in Tromsø, where he worked at Norway’s Arctic University. Several Russian citizens have been detained in Norway in recent weeks, mostly for possessing drones or allegedly photographing subjects covered by a photography ban. Most have since been released. European nations have stepped up security measures around key energy, internet and electricity infrastructure after underwater explosions ruptured two Baltic Sea gas pipelines built to carry Russian gas to Germany. The damaged Nord Stream pipelines off Sweden and Denmark released huge amounts of methane, a potent greenhouse gas, into the air. The Russian embassy in Oslo claimed that authorities there used drone and ship sightings, as well as incidents of Russians with cameras, to fuel a “spy frenzy”.