Seoul calls Russian ambassador as Korean tensions rise

Earlier on Friday, the powerful sister of North Korean leader Kim Jong-un issued a vague threat of retaliation after South Korean activists flew balloons carrying anti-Pyongyang propaganda leaflets across the border.

South Korea's military said it had fired warning shots the previous day to repel North Korean soldiers who briefly crossed the rivals' land border for the third time in June.

That came two days after Moscow and Pyongyang reached a pact vowing mutual defence assistance if either is attacked, and a day after Seoul responded by saying it would consider providing arms to Ukraine to fight Russia's invasion.

South Korean Vice-Foreign Minister Kim Hong-kyun summoned Russian ambassador Georgy Zinoviev to protest the deal between Russian President Vladimir Putin and Kim Jong-un and called for Moscow to immediately halt its alleged military co-operation with Pyongyang.

The minister stressed that any co-operation that helped the North build its military capabilities would violate UN Security Council resolutions and pose a threat to the South's security.

Zinoviev told Korean officials that any attempts to "threaten or blackmail" Russia were unacceptable and that his country's agreement with North Korea was not aimed at specific third countries.

Leaflet campaigns by South Korean civilian activists in recent weeks have prompted a resumption of Cold War-style psychological warfare along the Koreas' border.

The South Korean civilian activists, led by North Korean defector Park Sang-hak, said it sent 20 balloons carrying 300,000 propaganda leaflets, 5000 USB sticks with South Korean pop songs and TV dramas, and 3000 US dollar bills from a border town on Thursday night.

In a statement on North Korean state media, Kim Yo-jong, one of her brother's top foreign policy officials, called the activists "defector scum" and issued an apparent threat of retaliation.

"When you do something you were clearly warned not to do, it's only natural that you will find yourself dealing with something you didn't have to," she said.

After previous leafletting by South Korean activists, North Korea launched more than 1000 balloons that dropped tonnes of rubbish in South Korea, smashing roof tiles and windows and causing other property damage.

In response, South Korea resumed anti-North Korea propaganda broadcasts with military loudspeakers installed at the border for the first time in years, to which Kim Yo-jong, in another statement, warned Seoul was "creating a prelude to a very dangerous situation".

Korean tensions are at their highest in years as Kim Jong-un accelerates his nuclear weapons and missile development and attempts to strengthen his regional footing by aligning with Russian President Vladimir Putin against the US-led West.

South Korea, which has a well-equipped military backed by the United States, says it is considering upping support for Ukraine in response.

Seoul has already provided humanitarian aid while joining US-led economic sanctions against Moscow, but it has not directly provided arms.

Putin told reporters in Hanoi, Vietnam, on Thursday that supplying weapons to Ukraine would be "a very big mistake", and said South Korea "shouldn't worry" about the pact if it was not planning aggression against Pyongyang.

In the latest border incident, South Korea's Joint Chiefs of Staff said several North Korean soldiers engaged in construction work briefly crossed the Demilitarised Zone on Thursday morning.

The South Korean military broadcast a warning and fired warning shots, after which the North Korean soldiers retreated.

Seoul believes recent border intrusions were not intentional because the North Korean soldiers did not return fire and retreated after the warning shots.

The South's military has observed the North deploying numerous soldiers to build anti-tank barriers and other fortifications along its border.

Australian Associated Press