CNN
 — 

Five North Korean drones crossed into South Korean airspace on Monday, prompting the South Korean military to deploy fighter jets and attack helicopters, the country’s defense ministry said.

The ministry said South Korea’s military fired shots at the drones, but added it couldn’t confirm whether any drones were shot down.

Lee Seung-oh, a South Korean defense official, said four of the drones flew around Ganghwa island and one flew over capital Seoul’s northern airspace.

“This is a clear provocation and an invasion of our airspace by North Korea,” Lee said during a briefing. In response to the airspace violation, Lee said, the South Korean military sent its manned and unmanned reconnaissance assets to the inter-Korean border region, with some of them crossing into the North Korean territory.

The assets conducted a reconnaissance mission, including filming North Korea’s military installations, Lee added.

The South Korean military first detected the drones in the skies near the northwestern city of Gimpo at around 10:25 a.m. local time Monday, according to the country’s defense ministry.

The last time a North Korean drone was detected below the inter-Korean border was in 2017, according to the South Korean defense ministry. At the time, South Korea said it had recovered a crashed North Korean drone that was spying on a US-built missile system in the country.

North Korea has aggressively stepped up its missile tests this year, often launching multiple weapons at a time. It’s fired missiles on 36 separate days – the highest annual tally since Kim Jong Un took power in 2012.

Most recently, North Korea launched two short-range ballistic missiles on Friday, according to South Korean officials. The missiles were fired from Pyongyang’s Sunan area into the waters between the Korean Peninsula and Japan.

The secretive country usually test-launches its missiles in this way, firing them at a lofted angle so that they land in the waters between the Korean Peninsula and Japan.

However, in October, it fired an intermediate-range ballistic missile (IRBM) at a normal trajectory that went over Japan for the first time in five years.

In November, it claimed to have launched a “new type” of ICBM, Hwasong-17, from Pyongyang International Airfield, a missile that could theoretically reach the mainland United States. And last week, Kim Yo Jong, Kim Jong Un’s sister and a top official in the regime, claimed in state media that North Korea was ready to test-fire an intercontinental ballistic missile (ICBM) at a normal trajectory, a flight pattern that could prove the weapons can threaten the continental United States.

The United States and South Korean experts have warned that Pyongyang could be preparing for a nuclear test, its first in more than five years. North Korea has been developing its nuclear missile forces in violation of United Nations Security Council resolutions, ramping up its activities since the last of three meetings in 2019 between Kim Jong Un and then-US President Donald Trump failed to yield any agreement.

In October, Kim warned his nuclear forces are fully prepared for “actual war.”

“Our nuclear combat forces… proved again their full preparedness for actual war to bring the enemies under their control,” Kim said in comments reported by the North’s state-run Korean Central News Agency.