South Korea will work with the United States and other countries to enforce the latest sanctions slapped against North Korea for carrying out nuclear and missile tests, a senior presidential official said Thursday.

"We plan to concentrate our diplomatic efforts to ensure" that a U.N. Security Council resolution is carried out to the letter to produce its desired effect," the official told reporters. He asked not to be identified, citing policy.

His comments came after the council unanimously adopted a new resolution to punish North Korea for its fourth nuclear test and long-range rocket launch.

The resolution, if implemented to the fullest, is expected to deal a blow to North Korea as it would cut off the country's access to hard currency.

The resolution mandates U.N. member states to inspect all cargo going in and out of North Korea. The official described the clause of the resolution as something that is "unimaginable." 

It also bans the North's exports of coal, iron and other mineral resources, a key source of hard currency that accounts for roughly half of the country's total exports.

North Korea has already been under U.N. sanctions for its three previous nuclear tests, although these have failed to deter the communist country's nuclear ambitions.

The official said China has decided that it cannot keep the situation as it is following the North's nuclear and missile tests, and this change of heart has led to the stronger U.N. sanctions.

China has worked out the resolution with the U.S., a clear signal that Beijing is serious about reining in North Korea's nuclear and missile programs.

China is North Korea's most important trading partner and key source of food and fuel, giving Beijing significant leverage over Pyongyang.

China has long been under fire from critics that it has been reluctant to enforce tougher measures against North Korea, apparently worried that such a move will destabilize its neighbor.

The presidential official said South Korea also gave an impetus to the U.N. resolution, citing its recent shutdown of the last-remaining economic project with North Korea.

South Korea has shuttered a factory park that it had jointly run with North Korea in the North's border city of Kaesong, cutting off a major revenue source for North Korea.

South Korea provided around $560 million in cash to North Korea in total since the two sides opened the factory park in 2004.

President Park Geun-hye has described the closure of the factory park as just the "beginning" of measures that South Korea and the international community will take against North Korea. (Yonhap)