The large armada was sent to the Thitu Island, a Philippine-held part of a large cluster of islands disputed between China , Taiwan, Malaysia, the Philippines and Vietnam, it said.
The fleet, which includes vessels from the navy, coastguard and dozens of fishing boats, is part of an effort to stop the Philippine government from continuing construction on the island, it added.
According to the report, the number of deployed ships surged on December 25, reaching 95 ships. The number has since dropped, reaching 42 vessels by January.
The Philippine government has been seeking to develop an airway on the island by building a breaching ramp since 2017.
The project was due to be finished by the end of last year, but officials say that it has been delayed because of extreme weather.