"The exercise has started today. We currently have the first big rotation underway," Colonel Henrik Elo from the Finnish Air Force, which hosts the exercise, told AFP.

For nearly two weeks, soldiers and fighter jets from 14 nations, 12 of which are NATO members, will take part in exercises, mainly over Sweden's northern regions.

"As the exercise progresses, the scenarios get progressively more difficult," Elo said.

After abandoning decades of military non-alignment, Finland -- which shares a 1,300-kilometre (800-mile) border with Russia -- became the newest member of NATO in April, though the Nordic country had been a partner of the trans-Atlantic military alliance since the 1990s.

The "Arctic Challenge Exercise", hosted biannually by Nordic countries since 2013, this year sees the Netherlands, Belgium, Britain, Italy, Canada, France, Germany, Switzerland, Denmark, the Czech Republic and the United States participating, in addition to the host countries.

"This is the biggest one of these exercises organised so far," Elo said.

The exercise will start with simulations of defensive operations to protect airspace from attackers, with offensive elements such as air-to-ground attacks introduced later on.

NATO's Airborne Warning and Control System aircraft (AWACS) -- which can monitor an area almost as big as Poland -- will also participate in the exercise.

Elo said that being able to "coordinate with our NATO allies and partners on the performance of the different equipment is really significant".

The US State Department has said that Secretary of State Antony Blinken is also due to travel to Finland this week.