North Korea warned it was prepared to risk “all-out war” as leader Kim Jong-un put his frontline troops on combat readiness to back up an ultimatum for South Korea to halt propaganda broadcasts across the border by Saturday afternoon. The warning came as military tensions on the divided Korean peninsula soared following a rare exchange of artillery fire on Thursday that put the South Korean army on maximum alert. “Our military and people are prepared to risk an all-out war not just to simply respond or retaliate, but to defend the system our people chose,” North Korea’s foreign ministry said in a statement early Saturday on the official KCNA news agency, according to the South’s Yonhap news agency. “The situation has reached the verge of war and can no longer be reversed,” it said, after the ultimatum for the South to switch off its loudspeakers by 5pm local time on Saturday afternoon (8.30am GMT) or face military action. Seoul said it would continue the broadcasts unless the North accepts responsibility for landmine explosions this month in the demilitarised zone (DMZ) that wounded two South Korean soldiers. Pyongyang denies it planted the mines. South Korean vice defence minister Baek Seung-joo said…