North Korea has stopped the shipments of its rare earth metals to China in retaliation of China's recent ban on the imports of the North's key export item, coal, a U.S. broadcaster reported Friday.

On Feb. 19, China introduced the step pertinent to the latest U.N. Security Council's Resolution 2321 to punish the North's fifth nuclear test in September. The Chinese punitive step was declared to be effective through the end of the year.

Adopted on Nov. 30, the resolution is aimed at significantly curtailing the North's coal exports -- a key source of hard currency for its nuclear program -- by putting a cap on its total export amount. The cap was set at whichever is lower between 7.5 million tons, or $400 million, which means a nosedive in the North's annual coal export revenue by more than 60 percent, or about $700 million.

"It's around Feb. 20 when the central government ordered to completely ban the exports of rare earth metals to China," Radio Free Asia said, citing a source in the North's North Hamkyong Province.

The ban is believed to be a countermeasure against China's suspension of North Korean coal imports, the source was quoted as saying.

"Iron ores from Musan and magnesia clinker from Dancheon are still shipped to China, and yet the exports of such rare earth metals as molybdenum from Musan and cobalt from Hoeryong are completely suspended," the source said.

Another source in the North's Ryanggang Province also said, "Our province wholly stopped metal exports to China, and they are all rare earth metals." (Yonhap)