Chinese authorities have stepped up security at the country's airports, following the disappearance of a plane travelling from Kuala Lumpur to Beijing.
Malaysia Airlines flight MH370 disappeared at 02:40 local time on Saturday (18:40 GMT on Friday) with 239 people on board. It had been expected to land in Beijing at 06:30 (22:30 GMT).
Malaysia's transport minister said there was no information on wreckage.