HAIKOU -- Chinese police are searching for 18 missing fishermen from China's southernmost province of Hainan after learning their fishing boat had been robbed on Thursday in South China Sea.

The captain of "Qionghai 08099" called his family on Thursday morning, saying the boat was robbed by an armed gang after it had broken down in waters near Nanshan Islands, an official with the provincial public security department told Xinhua on Saturday.

The official, who declined to give his name, said the local marine public security office had dispatched a coast guard vessel and mobilized local fishermen in search for fishermen and their boat.

Captain Xu Demin called his wife at 6:10 a.m. on Thursday, saying a group of men of unidentified nationality were robbing his boat and asking his wife to inform the police, said Wang Weihao, a police officer.

Twenty minutes later, Xu phoned his cousin, Xu Defu, saying that the robbers had left with his catch of fish, but that another unidentified vessel was approaching the"Qionghai 08099" and it too might be thieves, said Wang.

Xu's family has had no further contact with him since the second call, said Wang.