BEIJING (AP) — China’s Education Ministry issued a safety warning for Chinese students in the Philippines after what it said were a series of criminal incidents targeting them.

The brief warning Friday did not identify any specific incidents but told students to increase their safety awareness should they choose to study in the Philippines. The number of Chinese students in the country was not given but enrolments have fallen to just a few hundred in recent years, according to the Hong Kong newspaper South China Morning Post.

Relations between the governments of China and the Philippines are particularly tense due to disputes over maritime claims in the South China Sea, which China claims almost in its entirety. China has used water cannons and other non-lethal shipboard deterrents to drive off Philippine fishing boats.

Politically, China has dismissed a U.N.-backed court decision in The Hague that ruled out most of China’s claims in the South China Sea and has expressed resentment over close ties between the U.S. and Manila.

China often disrupts cultural and economic ties to register their discontent over actions by foreign governments.

In April, China issued a similar warning about the risk to Chinese students in the United States.