A reported Chinese ban on ship traffic around disputed gas fields in the East China Sea could violate the U.N. Convention on the Law of the Sea, Chief Cabinet Secretary Shinzo Abe said Monday.

Japan had requested confirmation from China of news reports saying Beijing has imposed the ban while Chinese workers lay pipelines and cables in the area, he said.

"We have expressed our concern. This notice, if implemented, may breach our sovereign rights and violate the U.N. Convention on the Law of the Sea," Abe told reporters.