Taiwan's spy chief said Monday that the island had received a warning of possible terrorist attacks in China as the mainland hold its annual parliamentary session.

National Security Bureau head Tsai De-sheng told a legislative committee Monday that the NSB passed on a warning of planned attacks against the Beijing airport and the city's subway system to Chinese authorities following its receipt on March 4.

It comes as China's National People's Congress holds its annual session, which opened March 5 and closes Thursday.

It also came three days after a knife attack by a group of people at a railway station in Kunming, China, left 29 people dead. Police also shot dead four of the attackers.

Tsai said the receipt of the warning prompted stepped up security measures at Taiwanese airports, particularly on Beijing-bound flights.

He said it had no connection to a Malaysia Airlines flight bound for Beijing that has been missing since early Saturday.