China has voiced firm opposition to illegal unilateral sanctions and the abuse of judicial means after Cuban Foreign Minister Bruno Rodriguez condemned Washington's indictment of former Cuban leader Raul Castro.

On Wednesday, the United States Department of Justice announced the unsealing of a superseding indictment charging Castro and five others in connection with the Cuban military's downing of two aircraft operated by "Brothers to the Rescue" 30 years ago.

Speaking at a regular news briefing in Beijing on Thursday, Foreign Ministry spokesman Guo Jiakun said China firmly supports Cuba in safeguarding its national sovereignty and dignity, and opposes external interference.

Guo said China always firmly opposes illegal unilateral sanctions that have no basis in international law and are not authorized by the United Nations Security Council.

He added that China opposes the abuse of judicial means, as well as any attempt by external forces to pressure Cuba under any pretext.

"The US should stop wielding the big stick of sanctions and judicial measures against Cuba, and stop resorting to threats of force," Guo said.