By Ruby Lian and Megha Rajagopalan
SHANGHAI/BEIJING (Reuters) - Chinese maritime authorities must "blacklist" 31 boats operated by a North Korean firm that came under U.N. Security Council sanctions this week, according to a Ministry of Transport document reviewed by Reuters - a signal that China is enforcing tough new curbs aimed at Pyongyang's banned nuclear program.
The notice, dated March 3, says maritime safety agencies must "urgently" determine whether 31 vessels belonging to Ocean Maritime Management Co (OMM) are in Chinese harbors or waters, and notify the ministry.
The latest U.N. sanctions, drafted by the United States and China, blacklist the vessels. The ministry's notice says authorities must not allow the vessels to enter Chinese harbors, adding the measures were part of the "exceedingly sensitive" work of enforcing the U.N. sanctions.
The ministry did not immediately respond to a request for comment outside normal business hours. OMM could not be reached for comment.
The U.N. sanctions, passed unanimously on Wednesday, punish North Korea following its fourth nuclear test, in January, as well as last month's satellite launch, which the United States and others say was really a test of ballistic missile technology.
Independent experts have frequently questioned China's resolve to enforce sanctions against North Korea, whose economy is heavily dependent on China. China has said it will enforce the measures "conscientiously".
The Philippines Coast Guard has banned one of the 31 OMM vessels, the 6,830 deadweight tonne (dwt) Jin Teng general cargo ship, from leaving port until safety deficiencies are put right, officials said on Friday.
Authorities this week also restricted how many vehicles could cross into North Korea each day via a bridge to the coastal Chinese city of Dandong, from 300-400 earlier to about 100, shopkeepers there said - a sign that sanctions are having some early impact.
The U.N. latest sanctions also ban North Korean exports of coal and iron ore other than for "livelihood purposes" and if proceeds do not go to fund the North's weapons programs - wording that leaves room for interpretation and continued trade.
North Korea was one of China's top sources for imported coal last year.
(Reporting by Ruby Lian and Megha Rajagopalan; Editing by Ian Geoghegan)