North Korea yesterday cut its military hotline to Seoul and put its million-man army at battle stations, ratcheting up tensions as South Korean and US troops began war games that Pyongyang warned could spark open conflict.

UN forces last week tried to counter North Korean claims that the exercises were a smokescreen for an invasion by promising to keep the hotline open, giving Pyongyang advance warning of anything that could cause a misunderstanding, reported the Financial Times.