The Chinese research deep-sea submersible Jiaolong with three people onboard dived to a depth of 5,057 meters in the Pacific Ocean on Tuesday, Xinhua said.
Jiaolong, named after a mythical sea dragon, dived below 4,000 meters last week as part of ongoing sea trials.
Tuesday's dive makes China the fifth country in the world after the United States, France, Russia and Japan which have equipment for manned dives to depths of more than 3,500 meters.
Chinese experts say dives at the depth of five kilometers will allow research on 70 percent of the ocean floor.
Engineers expect the submersible to dive even deeper, but the record-breaking attempt will be held no earlier than next year.
Xu Qinan, chief designer of the submersible, expects it to reach depths of 7,000 meters below sea level and be suitable for studying 99 percent of the ocean floor.
