North Korea has changed the names of its trading companies and falsified trade documents to avoid international sanctions and continue exporting weapons, a news report and an intelligence official said Wednesday.

The UN Security Council slapped tough sanctions on North Korea last year over its launch of a long-range rocket and a subsequent nuclear test, including the blacklisting of some North Korean companies suspected of involvement in weapons exports.

Since then, North Korea has changed the names of two of the companies — Korea Mining Development Trading Corp. and Korea Tangun Trading Corp. — to Gapmun Tosong and Jasongdang Trade, the Dong-aIlbo newspaper reported, citing South Korean and U.S. intelligence officials.

North Korea also is apparently transporting arms exports through China and using forged trade invoices, for example labelling torpedoes as fish processing equipment and rocket shells as oil boring machines, the newspaper said.

An official of South Korea's National Intelligence Service said the report appears to be true, but declined to give further details and asked not to be identified because it involves an intelligence matter.

The report came days after the U.S. government expanded its sanctions against North Korea by freezing assets of individuals, companies and organizations allegedly linked to the North's nuclear program.

The U.S. Treasury Department said President Barack Obama issued an executive order authorizing action against four North Korean individuals, three North Korean companies and five North Korean government agencies. The order took effect Monday.