South Korea said on Monday that North Korea flew "several" drones into its airspace, prompting Seoul to fire warning shots and scramble aircraft.

Tensions were heightened this year amid an unprecedented number of military tests. But Monday's incident is the first time since 2017 that Pyongyang's drones crossed into the South's airspace.

What did South Korea say?

South Korea's Joint Chiefs of Staff (JCS) said the military detected the drones at around 10 a.m. local time (0100 UTC).

"Several North Korean unmanned aerial vehicles invaded our airspace" in the border areas around the northwestern Gyeonggi province, the JCS added.

The Defense Ministry said that after firing warning shots, the military launched fighter jets and attack helicopters to shoot down the North Korean drones. It was not immediately clear if the drones were shot down.

In 2017, authorities discovered a suspected North Korean drone that crashed in South Korea. At the time, South Korean authorities said the drone photographed a US missile defense system in South Korea.

The incident came three years after suspected North Korean drones were found south of the border.

According to Seoul, North Korea has about 300 drones.

Record pace of drills

This year, Pyongyang has ramped up weapons testing with an unprecedented number of tests, launching more than 40 ballistic missiles.

North Korea fired two short-range ballistic missiles toward its eastern waters last Friday. The move was widely seen as retaliatory to joint South Korean-US military drills as Pyongyang views the exercises as an invasion rehearsal.

Pyongyang also recently claimed to have launched tests as part of developing its first military spy satellite and a new strategic weapon.

The International Atomic Energy Agency has warned that North Korea could be preparing for a nuclear test.

Earlier this year, the country's leader Kim Jong Un said this year that he wanted to have the world's most powerful nuclear arsenal.