Taiwan's spy chief revealed yesterday that the island's security officials had last week received a warning about possible terrorist attacks on the mainland.
National Security Bureau chief Tsai De-sheng told a legislative committee that the agency had passed on a warning of planned attacks on Beijing airport and the city's subway system to mainland authorities after receiving it on March 4.
Tsai did not specify how the warning, which came three days after a knife attack at Kunming railway station left 29 civilians dead, had been relayed to the bureau.
However, security chiefs were believed to have received the alert from Taiwan-based China Airlines, following a phone call to the airline earlier in the day from a man who said he wanted to warn of possible terrorist activity.
Claiming to work for an anti-terrorism organisation in France, the caller spoke in French at first but switched to Putonghua with a Cantonese accent when the airline's switchboard operator could not understand him.
China Airlines yesterday confirmed that a call was received on March 4. It said the information it received was passed to Taiwan's civil aviation authority and aviation police.
In a statement, the airline said: "China Airlines on March 4 received a call claiming to provide intelligence on terrorist organisations and which referred to mainland China, saying Beijing airport would see terrorist attacks."
There is no indication the warning was connected to the disappearance of Malaysia Airlines flight MH370, which vanished from radar screens in the early hours of Saturday.
Separately, on March 3 China Airlines circulated an unrelated "aviation security notice" to all staff, warning of a "significant risk of terrorist attacks and military actions against aviation", a spokeswoman said yesterday.
The spokeswoman said the notice was issued in the wake of the March 1 Kunming railway station attacks. The notice urged all of its staff on the mainland to "be aware of individual security".
The spokeswoman said security alerts were circulated from time to time but that they were not automatically issued during high-profile events such as the ongoing National People's Congress meetings in Beijing.
Meanwhile, Taiwanese President Ma Ying-jeou yesterday ordered the defence ministry and coastguard to join the search for missing Malaysia Airlines flight MH370.
Additional reporting by Lawrence Chung in Taipei