Twenty-three Chinese tourists and two crew members have survived after their boat sank in rough seas off eastern Malaysia but six people are still missing, a minister said on Sunday.
The sinking of the catamaran on Saturday, the first day of the Lunar New Year holiday, sparked a major air and sea search covering some 400 nautical square miles.
The operation would continue overnight to try to save five missing Chinese and one crew member, said Shahidan Kassim, minister in the Prime Minister's Department.
"We will deploy search assets that can operate at night, and continue our rescue operations to locate those who are still missing," he told a press conference in Malaysia's eastern state of Sabah on Borneo island.
All three crew members are Malaysians.
The boat had left Saturday morning from the Sabah state capital Kota Kinabalu en route for Pulau Mengalum, an island known for its pristine beaches and dive sites.
The boat owner reported it missing on Saturday evening.
The skipper and one of the two crew members were found alive earlier Sunday off a nearby island, before the discovery of the other survivors.
"According to the skipper, the boat was 'broken' after being hit by waves and sank," said Ahmad Puzi Kahar, head of the Malaysian Maritime Enforcement Agency, in a statement.
The tourists were tied together and were carried away by the current, Puzi said, without specifying whether they were wearing life jackets.
The search and rescue involved officers from the maritime agency, the police, the navy and the air force.
Malaysian navy chief Ahmad Kamarulzaman Ahmad Badaruddin said navy ships and a C130 aircraft were on site for the search.
It was "so sad as it happened on CNY (Chinese New Year)", he tweeted.
Roughs seas and strong winds hampered the search on Saturday night and Sunday, authorities said.
Prime Minister Najib Razak said he was closely monitoring developments.
Chinese President Xi Jinping "demanded all-out search and rescue efforts" by Malaysia, his country's official Xinhua news agency reported.
It added that an emergency team, led by an official from Beijing's national tourism administration, had been set up to handle the incident.
China's foreign ministry said its consulate in Kota Kinabalu had contacted Malaysian authorities and urged them to do everything they could to rescue the tourists.
"Yesterday was the first day of the Chinese Lunar New Year and it should have been a happy day. Unfortunately, such a bad thing happened," China's consul-general in Sabah, Chen Peijie, was quoted as saying by state news agency Bernama.
An earlier disaster involving Chinese visitors to Malaysia -- the unexplained disappearance of a Malaysia Airlines plane in March 2014 while en route from Kuala Lumpur to Beijing -- soured relations between the two nations for a time.
Most of the 239 people on board were Chinese, and Malaysian authorities were fiercely criticised for allegedly giving scanty or inaccurate information.
The latest incident came about a week after a boat tragedy off the southern Malaysian state of Johor.
Several bodies washed ashore at a beach near the east coast town of Mersing in Johor on Monday after a boat believed to be carrying some 40 Indonesian illegal immigrants capsized in rough seas.