UNITED NATIONS — The United Nations has dispatched an envoy to North Korea for a rare visit aimed at defusing tensions over Pyongyang’s intercontinental ballistic missile launch, as the US and South Korea began joint military exercises condemned by North Korea’s leader Kim Jong-un.

The unusual visit by Jeffrey Feltman, which begins on Tuesday and runs to Friday, comes less than a week after North Korea test-fired a ballistic missile believed capable of reaching the US.

On Monday, the US and South Korea launched their biggest-ever joint air exercise -- maneuvers slammed by Pyongyang as an "all-out provocation."

The five-day Vigilant Ace drill involves 230 aircraft, including F-22 Raptor stealth jet fighters, and tens of thousands of troops, Seoul’s air force said.

Pyongyang sent tensions soaring on the Korean Peninsula five days ago when it announced it had successfully test-fired a new ICBM, which it says brings the whole of the continental US within range.

Analysts say it is unclear whether the missile survived re-entry into the earth’s atmosphere or could successfully deliver a warhead to its target – key technological hurdles for Pyongyang.

A Cathay Pacific crew spotted what was "suspected to be the re-entry" of the missile as they flew from San Francisco to Hong Kong, the airline said.

In a separate message to staff, Cathay general manager Mark Hoey said the crew described seeing the missile "blow up and fall apart," The South China Morning Post reported.

UN envoy to break logjam?

North Korea has staged six increasingly powerful atomic tests since 2006 -- most recently in September -- which have rattled Washington and its key regional allies South Korea and Japan.

Pyongyang faces tough international sanctions as a result of its unwillingness to stop its nuclear and ballistic missile programmes.

Ahead of his visit to Pyongyang, Feltman -- the UN under-secretary-general for political affairs -- was in Beijing on Monday. 

Once in the North, Feltman will discuss "issues of mutual interest and concern" with officials, UN spokesman Stephane Dujarric said, adding he was unable to say whether Feltman will meet with Kim.

It will be Feltman’s first visit to North Korea since he took office five years ago, and the first by a UN under-secretary-general in more than seven years.

The UN envoy is planning to see foreign diplomats and UN workers in the North on humanitarian missions, Dujarric said. — AFP