North Korean leader Kim Jong-Un has ordered his frontline troops on to a war footing from Friday, as military tensions with South Korea soared following a rare exchange of artillery shells across their heavily fortified border. 

The North’s official KCNA news agency said the move came during an emergency meeting late on Thursday of the powerful central military commission (CMC) of which Kim is the chair.

During the meeting, Kim ordered frontline, combined units of the Korean People’s Army (KPA) to “enter a wartime state” from 5pm (9.30am BST) on Friday. The troops should be “fully battle-ready to launch surprise operations” while the entire frontline should be placed in a “semi-war state”, KCNA quoted Kim as saying.

The CMC meeting came hours after the two Koreas traded artillery fire on Thursday, pushing already elevated cross-border tensions to dangerously high levels.

North Korea followed up with an ultimatum sent via a military hotline that gave the South 48 hours to dismantle loudspeakers blasting propaganda messages across the border or face further military action. The ultimatum expires at 5pm on Saturday. 

Seoul began blasting anti-North Korean propaganda from loudspeakers on the border on 10 August, resuming a tactic that both sides had stopped in 2004. South Korean president Park Geun-hye told defence officials to “react firmly” to North Korean provocations, according to a spokesman. 

“Our military has stepped up monitoring and is closely watching North Korean military movements,” the South’s defence ministry said.

The defence ministry dismissed the threat from the North and said the broadcasts would continue. Neither side had reported any damage or casualties by early Friday morning.