Chinese President Xi Jinping has demanded all-out search and rescue efforts for the 28 Chinese nationals on a boat that sank off Malaysia's Sabah state on North Borneo on Saturday evening.

According to an official release issued on Sunday, Xi asked the Ministry of Foreign Affairs and the Chinese Embassy in Malaysia to maintain close contact and cooperation with authorities of Malaysia, and China's transport and tourism authorities to activate emergency measures immediately to assist the rescue.

Premier Li Keqiang also urged the search and rescue efforts to ensure that not a single Chinese national will be left unaccounted for.

Chinese Consulate General's Office based in Kota Kinabalu, the state capital, said in the latest briefing that 25 Chinese have been rescued so far.

The office said the survivors were rescued by several vessels and will be sent to the nearby Labuan island for medical check-up.

The boat carrying 31 people, including 28 tourists from China, went missing on Saturday after sailing from Kota Kinabalu to Pulau Mengalum, a popular tourist island, some 60 km west to Kota Kinabalu.

Given a surging number of tourists and travellers during the ongoing Spring Festival holiday, security and emergency response measures must be increased and safety awareness must be enhanced among the public, Xi said.

Premier Li pledged measures to guarantee rights and interests of the Chinese citizens and inform their families about the progress in the rescue.