The UN Security Council is weighing a response to North Korea's failed test-firing of ballistic missiles, diplomats said Thursday following emergency closed-door talks in New York.

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

"We are looking at a response," said China's Ambassador Liu Jieyi, who holds the council presidency this month.

Japanese Ambassador Motohide Yoshikawa said his government "condemns the series of grave and very clear violations of Security Council resolutions."

"This is a threat to Japan's national security," he said.

Yoshikawa added that council diplomats were unanimous in condemning the latest launches during the closed-door meeting and that they were preparing to issue a statement.

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 ruling 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.