The UN Security Council hastily met for closed-door talks on Thursday on North Korea's failed test-firing of ballistic missiles, the latest defiance from Pyongyang of UN resolutions.

The consultations were urgently requested by the US following North Korea's unsuccessful launch of two missiles and growing fears that the regime is preparing to conduct a fifth nuclear test.

North Korea has made three unsuccessful bids in two weeks to test-fly a Musudan medium-range missile, which is capable of striking US bases on the Pacific island of Guam.

The first effort on April 15 - the birthday of founding leader Kim Il-Sung - ended in what the Pentagon described as "fiery, catastrophic" failure, with the missile apparently exploding just after take-off.

South Korean military officials say the North is desperate to register a successful launch ahead of next week's party congress, at which leader Kim Jong Un is expected to take credit for pushing the country's nuclear weapons program to new heights.

The Security Council has repeatedly condemned the missile launches and stressed that they violated UN resolutions that bar Pyongyang from developing nuclear and ballistic missile technology.

In March, the Security Council imposed the toughest sanctions to date on North Korea after it carried out its fourth nuclear test and fired a rocket that was seen as a disguised ballistic missile test.

It was the fifth set of UN sanctions to hit North Korea since it first tested an atomic device in 2006.