North Korea’s coal exports shriveled to zero in April, according to data released by the U.N. Security Council’s committee on sanctions on the country.

The data attests to the efficacy of the 15-member council’s sanctions resolution adopted last November over the country’s fifth and largest nuclear test earlier in the year. Coal is the North’s biggest export, with China the main buyer.

China in February suspended all imports of coal from North Korea for at least the remainder of the year as part of efforts to implement U.N. sanctions against the country.

The resolution put a ceiling on the North’s coal exports at $400.9 million, or 7.5 million tons per year, whichever is lower, starting on Jan. 1. The measure is expected to cut the country’s hard currency revenues by at least $700 million annually.