North Korea fired several short-range projectiles into the sea just hours after the United Nations slapped sanctions on Pyongyang for its recent nuclear test and long-range rocket launch.

South Korea's defence ministry made the announcement shortly after Seoul approved its first legislation on human rights in North Korea

The South Korean bill's passage came as the UN Security Council was unanimously approving its toughest sanctions against North Korea in 20 years.

A total of 212 South Korean MPs voted for the bill and 24 others abstained. It becomes law when it is endorsed by the cabinet council, which is considered a formality.

North Korea's state media has warned that enactment of the law would result in "miserable ruin".

South Korea defence spokesman Moon Sang Gyun said the projectiles were fired from the eastern coastal town of Wonsan.

The projectiles could be missiles, artillery or rockets, according to the defence ministry.

Yonhap news agency reported North Korea fired eight or nine projectiles that flew about 60 miles before landing in the sea.

North Korea routinely test-fires missiles and rockets, but it often conducts more weapons launches when angered at international condemnation.

Thursday's launch was a "low-level" response to the UN sanctions, with Pyongyang unlikely to launch any major provocation until a landmark ruling Workers' Party convention in May, according to Yang Moo-jin, a professor at the University of North Korean Studies in Seoul.

Pyongyang conducted its fourth nuclear test in January, making the widely disputed claim that it successfully detonated a hydrogen bomb.

Last month, it put a satellite into orbit on a long-range rocket that the UN and others see as a cover for a test of banned ballistic missile technology.

The new UN sanctions include mandatory inspections of cargo leaving and entering North Korea by land, sea or air.

There is also a ban on all sales or transfers of small arms and light weapons to Pyongyang, and the sanctions provide for the expulsion of diplomats from the North who engage in "illicit activities".