South Korea and the wider world are watching the nuclear North
The United Nations Security Council has voted unanimously to impose tougher sanctions on communist North Korea.
The move follows a nuclear test carried out by the North Koreans last month, in defiance of previous UN resolutions.
The sanctions include the inspection of North Korean ships, a wider ban on arms sales and other financial measures.
The US deputy ambassador at the UN, Rosemary DiCarlo, said the new vote was a strong and united response to North Korea's "unacceptable behaviour".
She said: "North Korea chose a path of provocation. This resolution will give us new tools to impair North Korea's ability to proliferate, and to threaten international stability."
'Appropriate and balanced'
The Chinese ambassador, Zhang Yesui, said the resolution showed the "firm opposition" of the world to North Korea's nuclear ambitions.
"We strongly urge the DPRK (North Korea) to honour its commitment to de-nuclearisation, stop any moves that may further worsen the situation, and return to the six-party talks," the ambassador said.
He described the resolution as "appropriate and balanced" but said measures authorising states to inspect cargo should be handled prudently, with no use - or threat - of force.
He said North Korea's nuclear test had jeopardised security and stability in the region.
China and Russia have been reluctant to support punitive measures against North Korea in the past.
The new resolution, which was drafted by the Americans, is now binding in international law.
It authorises UN member states to inspect North Korean cargo being transported on land, at sea and by air, and to destroy any goods suspected of being connected to weapons of mass destruction.
In addition, it broadens the arms embargo against North Korea, banning the sale by the North Koreans of heavy and small arms.
North Korea carried out a nuclear test - its second - on 25 May. It then launched a number of short-range missiles.
The UN Security Council approves tough new sanctions on North Korea
The North has previously warned that it will use nuclear weapons in a "merciless offensive" if provoked.
BBC Diplomatic Correspondent, Jonathan Marcus, says it is far from clear if the latest moves at the UN will achieve the desire outcome of bringing North Korea back to the negotiating table.
He says much depends on the actions of individual governments, and it is clear that China remains deeply uneasy about cargo inspections.
All eyes, he says, will be on North Korea's reaction, with many analysts fearing it may respond with more missile tests and bluster.