SOUTH KOREA summoned the Russian ambassador to protest against the country’s new defence pact with North Korea today, following a seemingly accidental incursion by North Korean troops over the border.

The powerful sister of North Korean leader Kim Jong Un issued a vague threat of retaliation today morning after South Korean activists flew balloons carrying anti-Pyongyang propaganda leaflets across the border, and 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 this month.

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.