North Korea fires ballistic missile as Blinken arrives in South

North Korea on Monday has fired a missile just as US Secretary of State Antony Blinken visited South Korea, where he sought a stable course on foreign policy as political turmoil engulfs the US ally.

Blinken visited just as investigators were trying to arrest conservative President Yoon Suk-yeol, who has entrenched himself in his residence after being impeached for a failed attempt to impose martial law.

In a reminder of common challenges that go beyond domestic politics, North Korea on Monday fired a ballistic missile into the sea just as Blinken was holding meetings in Seoul, according to the South Korean military.

"Our military detected one projectile presumed to be a intermediate-range ballistic missile" launched toward the East Sea, South Korea's military said, referring to the body of water also known as the Sea of Japan.

After the missile flew around 1,100 kilometres (680 miles), the military said Seoul "strengthened surveillance and vigilance" for any more launches.

The missile appeared to have fallen into the water, according to Japan.

Seoul was "in close coordination with the US and Japan" about the launch, the South's military added.

The test comes two weeks before the inauguration of President-elect Donald Trump, who in his last term sought to woo North Korea with a unique personal diplomacy.