North Korea has threatened "strong" retaliation against Japanese sanctions as the UN considers what action it will take against the closed Communist state which claimed to have tested a nuclear bomb Monday.

"We will take strong counter-measures," warned Song Il Ho, North Korea's ambassador in charge of talks with Japan, when asked about Tokyo's unilateral sanctions imposed yesterday, including a ban on North Korean shipping.

"We never speak empty words," Mr Song warned in an interview with Japan's Kyodo news agency.

|PIC1|Anxiety has engulfed the region since Monday's claimed nuclear test and North Korea's threats will further unsettle Japan and other countries in close proximity to the reclusive state.

Earlier on Wednesday, North Korea's second most powerful leader also threatened more nuclear tests if the US remained "hostile".

In response to Monday's claim, Japan has imposed tough new sanctions on North Korea, including a total trade ban on North Korea, with all its ships denied entry to Japanese ports.

The sanctions will also prevent almost all North Koreans from entering Japan.

China's president, Hu Jintao, will hold talks in Beijing tomorrow with his South Korean counterpart, Roh Moo-Hyun, to discuss a common response to the crisis.

China has yet to say whether it will back sanctions but given that the country borders with North Korea and is regarded as its closest ally, China plays a crucial role in any agreement and implementation of sanctions.

Meanwhile, the US continues to lead the wider international efforts to get the United Nations to impose separate measures.

President Bush has this week assured reporters that Washington remains committed to diplomacy, and has no intention of attacking. But he said the US "reserves all options to defend our friends in the region".

UN Secretary General Kofi Annan has urged the US to hold one-on-one talks with North Korea, but Washington has refused to pursue this line of action so far.

The UN Security Council will meet tomorrow to discuss the possible sanctions, while the US has issued a revised draft resolution which mandates economic and trade sanctions coupled with an arms embargo.

The text invokes Chapter Seven of the UN Charter, meaning the sanctions would be mandatory and failure to comply could result in legal military action.