The US government has slapped new sanctions on North Korea, targeting illegal trade in arms, drugs and luxury goods, as it steps up the pressure over the sinking of a South Korean warship.

The Treasury Department announced Monday it was imposing sanctions on four people and eight organizations accused of aiding the secretive communist government through illicit trade.

President Barack Obama issued an order freezing assets and imposing travel bans, in the latest action over the sinking of the South Korean navy ship in March which Washington and Seoul have blamed on North Korea.

Obama also expanded the scope of US sanctions to cover those involved in the trade in arms, drugs and luxury goods to and from the dirt-poor nation.

Among those targeted was a secretive branch of the Korean Workers' Party, known as Office 39, which is suspected of selling methamphetamine in China and South Korea and acquiring luxury items for North Korea's leaders.

The group is thought to be involved in a failed attempt to buy two Italian-made luxury yachts worth more than 15 million dollars for North Korea's reclusive leader, Kim Jong-Il.

"North Korea's government helps maintain its authority by placating privileged elites with money and perks such as luxury goods like jewelry, luxury cars and yachts," said the Treasury Department's sanctions chief Stuart Levey.

Among those also targeted were the head of North Korea's intelligence agency Kim Yong-Chol, who has been linked to the March torpedo attack that killed 46 people on the South Korean corvette. Pyongyang denies any role in the attack.

Green Pine Associated Corporation, a group said to be controlled by Kim Yong-Chol's intelligence agency, was also sanctioned.

The organization was accused of "exporting arms or related materiel from North Korea," and is said to specialize in the production of maritime military craft and armaments.

"(Green Pine) has exported torpedoes and technical assistance to Iranian defense firms" the Treasury department said.

Other individuals, including two members of the North Korea's General Bureau of Atomic Energy were also sanctioned.

Others targeted included the head of North Korea's atomic energy bureau Ri Je-son and Ri Hong-Sop, who according to the United Nations, once ran the controversial Yongbyon Nuclear Research Center.

The center is suspected of producing fissile materiel used in nuclear weapons testing.

Talks aimed at ridding North Korea of nuclear weapons have been on hold since Pyongyang walked out of a multinational forum in 2009, but on a visit to China, the ailing Kim Jong-Il reportedly backed the resumption of negotiations.

Chinese television quoted Kim -- who reportedly returned home on Monday -- as saying Pyongyang's stance on ridding the peninsula of nuclear weapons was unchanged and the country "is not willing to see tensions on the peninsula".

Kim pledged to remain in close consultation with China and hoped for the "early resumption" of the six-party nuclear disarmament talks that also include South Korea, the United States, Japan and Russia, it said.

State media in China, North Korea's main ally and economic lifeline, called on the United States and its allies not to "bully" Pyongyang if they wanted to ease regional friction.

"Living in the shadows of South Korea, Japan and the US, North Korea has to wrap itself up tighter in order to fend off military threats, and threats of political and cultural infiltration," the Global Times said in a commentary.

"North Korea's opening-up will help relieve tensions in northeast Asia. But the knot does not only lie on the North's side. Other countries in the region must redouble their efforts to untangle the knot," said the Chinese paper.

"These three nations should not bully North Korea any more."

The North Korean leader rarely travels abroad but it was his second visit this year to China, also host of the six-party talks which began in 2003.

The North walked out in April 2009 and staged its second atomic weapons test a month later.

burs-txw/mtp