SEOUL: North Korea has bolstered its defences against a "hostile" United States with its third nuclear test, it said on Thursday, noting that countries that had bowed to U.S. pressure to abandon their nuclear plans had suffered "tragic consequences".

The North carried out its largest nuclear test to date last week, in defiance of U.N. resolutions, prompting warnings of tougher sanctions for the isolated and impoverished state and its young ruler, Kim Jong-un.

Libya abandoned its nuclear programme in 2003 in a bid to mend relations with the United States and later saw leader Muammar Gaddafi overthrown in an uprising that was eventually supported militarily by Washington.

In apparent reference to Libya, North Korea said it never backed down.

"The tragic consequences in those countries which abandoned halfway their nuclear programs... clearly prove that the DPRK (Democratic People's Republic of Korea) was very far-sighted and just when it made the (nuclear) option," North Korea's KCNA news agency said.

North Korea has told China, its sole major ally, that it plans to stage more nuclear tests, according to a source with close connections to the top leadership in both countries.

It staged the latest test in response to tighter U.N. sanctions imposed in January after the country launched a long-range rocket last year in a move that critics said was designed to prove technology for an intercontinental ballistic missile.

North Korea has recently stepped up its rhetoric against South Korea, threatening to destroy its rich, democratic neighbour.

Most military assessments suggest that North Korea would lose any war against the U.S.-backed South and that its leaders would not risk a major conflict.

In 2010, North Korea was blamed for sinking a South Korean naval vessel and in the same year it shelled a South Korean island, killing four people, including two civilians.