US military drills 'will trigger nuclear response'

North Korea vowed to respond with "powerful nuclear deterrence" to the joint US and South Korean military exercises poised to begin today, saying the drills would prompt a "retaliatory sacred war".

The allies' defence chiefs said the drills would send a clear message to Pyongyang to stop its "aggressive" behaviour. North Korea has been blamed for the deaths of 46 South Koreans in the sinking of the warship Cheonan in March. North Korea strongly denies any involvement.