North Korea's May nuclear test few kilotons - U.S.

WASHINGTON (Reuters) - The United States has determined that the nuclear test conducted by North Korea last month yielded an explosion of a few kilotons, the U.S. Office of the Director of National Intelligence said on Monday.

"The U.S. intelligence community assesses that North Korea probably conducted an underground nuclear explosion in the vicinity of Punggye on May 25, 2009," the office said in a statement. "The explosion yield was approximately a few kilotons."

North Korea's first nuclear test, in 2006, was about one kiloton.

Shortly after this year's blast, Russia said it estimated the explosion at about 20 kilotons, or about equal to the U.S. atom bomb dropped on Nagasaki in Japan in World War Two.

The Vienna-based Comprehensive Test Ban Treaty Organization then assessed the strength of the test to be much smaller, saying it was just slightly larger than the 2006 test.

U.S. intelligence officials are still analyzing the nuclear explosion, the statement said.

North Korea has raised tensions in the past month by test-firing missiles, restarting a plant to produce arms grade plutonium and holding the May nuclear test, which put it closer to having a working nuclear bomb.

Its latest announcement on Saturday to restart a uranium enrichment program and weaponize its plutonium came in response to new U.N. sanctions agreed on Friday.

U.S. Secretary of State Hillary Clinton has said North Korea's "continuing provocative actions are deeply regrettable."

State Department spokesman Ian Kelly said on Monday North Korea should abandon all its nuclear programs in a "complete, verifiable and irreversible manner."