North Korea 'on combat alert'

North Korea has reportedly ordered its armed forces to be placed on combat alert amid rising tensions on the Korean peninsula following the March 26 sinking of a South Korean naval vessel.

The order came directly from North Korea's leader, Kim Jong-il, South Korea's Yonhap news agency said on Tuesday, quoting sources inside the North.

There was no reference to the order on North Korean media monitored in the South, nor any immediate comment from South Korean officials.

North Korea has previously threatened "all-out war" in response to any moves to punish it for the sinking.

The report comes a day after the United Nations secretary-general joined the US in ratcheting up pressure on North Korea, calling for action from the Security Council in response to the alleged torpedo attack on a South Korean patrol ship that left 46 sailors dead.

Speaking at UN headquarters in New York, Ban Ki-moon said there was "overwhelming and deeply troubling" evidence that Pyongyang was behind the March 26 sinking of the Cheonan off the west coast of the Korean peninsula.