A foreign ministry statement said South Korea, a key economic supporter of its communist neighbour, "welcomes and supports" the resolution adopted unanimously Saturday by the UN Security Council.
"The government, as a United Nations member, respects the UN Security Council resolution and confirms it will sincerely implement this," it said.
Prime Minister Han Myeong-Sook promised to cooperate closely with the UN "and cope with this incident in a cool-headed and resolute manner".
"North Korea should bear all the consequences of the nuclear test," she said at a festival for defectors from the North. "It is an unpardonable and provocative act that threatens stability in Northeast Asia and the global order."
Protesters burnt North Korean flags during a rally in a Seoul park.
Although North Korea said last week that any tough sanctions would be seen as a "declaration of war", a glimmer of hope remained for diplomacy.
Russian Deputy Foreign Minister Alexander Alexeyev, Moscow's top nuclear negotiator, met his South Korean counterpart Chun Yung-Woo in Seoul late Sunday to discuss efforts to revive the six-nation disarmament talks.
Alexeyev, who met last week with his North Korean counterpart Kim Kye-Kwan in Pyongyang, has said the North wants the talks to resume.
"The North Korean side repeatedly insisted that the six-sided process should continue, that it is not rejecting six-sided negotiations, and that the aim of the full denuclearisation of the Korean peninsula remains," he said, according to Russia's Interfax news agency.
Alexeyev declined to comment to reporters before the meeting. His country, the two Koreas, China, Japan and the United States held several rounds of talks on scrapping North Korea's nuclear programme.
The foreign ministry statement, which reiterated Seoul's policy never to tolerate a nuclear-armed North Korea, urged it "to return immediately to six-nation talks" following its declared test on October 9.
At the talks in September last year, the North agreed to give up its nuclear program in exchange for energy and economic aid and security guarantees. But it has boycotted the forum since November in protest at US financial restrictions.
The UN Security Council, which imposed missile-related sanctions on the North following its July missile tests, on Saturday broadened those measures.
The new resolution demands the elimination of all nuclear weapons, weapons of mass destruction and ballistic missiles.
It provides for a travel ban on officials working on such programmes and calls for a ban targeting missiles, tanks, large artillery systems, warships and combat aircraft.
It also provides for inspection of cargo to and from the communist state.
But Kim Geun-Tae, chairman of South Korea's ruling Uri Party, urged Seoul not to take part in cargo searches for fear of sparking an armed clash.
South Korea has said its "sunshine" engagement policy with the North is under threat but has not elaborated.
Seoul is a major aid donor and also operates two inter-Korean projects -- the Kaesong industrial estate and the Mount Kumgang tourist resort -- which earn the cash-strapped North tens of millions of dollars a year.
Last year it was the North's biggest food donor after China.
"The new UN resolution is irrelevant to the projects in Kaesong and Kumgang," a senior unification ministry official told AFP on condition of anonymity, adding Seoul would push ahead with both.
The main opposition party and street protesters are demanding an end to the aid as well as to the Kaesong and Kumgang projects. Critics say they could help finance the nuclear programme and other weapons of mass destruction.

Copyright AFP (Agence France-Presse), 2006