The United Nations on Wednesday adopted the toughest sanctions to date on North Korea in response to its fourth nuclear test and rocket launch, prompting Pyongyang to respond with a show of military strength.

The Security Council unanimously passed a resolution imposing new sanctions after seven weeks of arduous negotiations between the United States and China, Pyongyang's sole major ally.

All eyes are now on China and Russia to see if they fully enact the sweeping measures.

The sanctions break new ground, requiring all countries to inspect cargo destined for and coming from North Korea, in all airports and sea ports.

They also ban or restricts exports of coal, iron and iron ore and other minerals from North Korea, and prohibit the supply of aviation fuel including rocket fuel.

North Korea earns about $1 billion per year in coal exports -- a third of all export revenues -- and about $200 million annually from iron ore sales, US Ambassador Samantha Power told the council.

US President Barack Obama welcomed the measures as "a firm, united, and appropriate response" to the January 6 nuclear test and February 7 rocket launch.

"The international community, speaking with one voice, has sent Pyongyang a simple message: North Korea must abandon these dangerous programs and choose a better path for its people," Obama said in a statement.

North Korea responded with a defiant display of military strength, launching a series of short-range projectiles into the sea off its east coast just hours after the resolution was adopted.

South Korea's defence ministry said it was analysing whether they were missiles, rockets or artillery shells.

Under Wednesday's resolution, banking restrictions will be tightened and governments will be required to ban flights of any plane suspected of carrying contraband destined for North Korea.

"These are among the toughest measures we have agreed against any country in the world, certainly the toughest ever against the DPRK," said British Ambassador Matthew Rycroft, referring to North Korea by its official acronym.

A total of 16 individuals and 12 entities were added to a UN sanctions blacklist, including North Korea's NADA space agency and its spy agency, the Reconnaissance General Bureau.

UN member states will expel North Korean diplomats engaged in smuggling or other illegal activities.

Luxury watches, snowmobiles, recreational watercraft such as Sea-Doos and sports equipment are banned from sale to North Korea, in sanctions targeting Pyongyang's elites.

- Making sanctions bite -

South Korean President Park Geun-Hye said she hoped the "unprecedentedly tough" sanctions would push Pyongyang into finally abandoning its nuclear weapons programme.

The resolution sends "a strong message from the international community seeking peace on the Korean peninsula," Park said.

Japanese Prime Minister Shinzo Abe urged Pyongyang to refrain from any fresh provocations, while Tokyo's ambassador to the UN, Motohide Yoshikawa, stressed that "the heart of the matter now is implementation" of the sanctions by China, North Korea's largest trading partner, and other countries.

Power also called for a "robust and unyielding" follow-up to ensure the sanctions bite and singled out Russia and China as key players.

Chinese Ambassador Liu Jieyi said the resolution should "be a new starting point and a stepping stone" for renewed talks on dismantling North Korea's nuclear program.

Russia echoed that view, with Ambassador Vitaly Churkin saying the resolution is designed to "shut down as much as possible the financing" of North Korea's weapons program to push Pyongyang back to the negotiating table.

During the weeks of negotiations, China had been reluctant to endorse harsh sanctions out of concern that too much pressure would trigger the collapse of the pariah regime, creating chaos on its border.

China's ambassador renewed Beijing's opposition to plans by South Korea and the United States to deploy a new missile defense system on the Korean peninsula, saying it undermines efforts to re-start Korea talks.

The US Treasury Department separately announced sanctions against two entities and 10 individuals with ties to North Korea's weapons programs.

The sanctions resolution did not target oil deliveries to North Korea and allows for exemptions to some export bans if a government can show that the revenue will not be used to develop North Korea's military programs.

China, and to a lesser extent Russia, "will find loopholes, they always have," to avoid fully implementing UN sanctions, said Roberta Cohen, an expert on North Korea at the Brookings Institution.

But Beijing "sees the mobilization of alliances, strong military alliances between the United States, South Korea and Japan and it sees that it can't go on the way it has," she added.

The latest resolution ushered in the fifth set of UN sanctions to hit North Korea since it first tested an atomic device in 2006.