Hong Kong air traffic controllers told Taiwan there was danger until further notice on a flight path to Taiwanese-controlled islands in the South China Sea, Taipei said on Friday, a case that has raised fears Beijing may try and blockade the islets. Tensions over the Pratas Islands, in the northern part of the contested South China Sea, have spiked in recent weeks, with China carrying out several military exercises near them. The Pratas are only lightly defended by Chinese-claimed Taiwan. On Thursday, Taiwan said a regular civilian charter flight had to abandon its trip to the Pratas when Hong Kong air traffic controllers told the captain there were “dangerous activities” happening below 26,000 feet and the aircraft could not enter. Hong Kong’s Civil Aviation Department said they had told Taiwan air traffic controllers of the minimum safe altitude to be observed for the flight, and that Taiwan had then responded that they had cancelled the request to enter the Hong Kong flight information region. But late on Friday Taiwan’s Civil Aeronautics Administration published a full transcript of the conversation between the air traffic controllers. “The danger area is, eh, now on until further notice,” the Hong Kong controller says, declining to answer a question on whether there were military exercises happening. Asked whether there was a NOTAM, or “notice to airmen” filed to alert aircraft pilots of potential hazards, the Hong Kong controller responds: “eh, no”. Then asked whether to confirm they would not allow the flight in, the Hong Kong controller says: “Affirmative, the altitude is not safe for danger after Hong Kong at this level”. Finally, when asked when the flight could proceed to the Pratas Islands, the Hong Kong controller answers: “OK, Hong Kong is not able to advise right now, we’ll let you know”. Hong Kong’s Civil Aviation Department said it had nothing to add beyond its initial statement. The Pratas flights carry mainly Taiwan defence and coast guard personnel. Taiwan Premier Su Tseng-chang told reporters on Friday they were trying to find out whether China was behind the move. The Civil Aviation Administration of China did not answer questions submitted by Reuters. Johnny Chiang, leader of Taiwan’s main opposition Kuomintang party, asked on his Facebook page whether China had just dangerously ramped up the stakes. “Does this mean that the Communist’s military has already begun joint blockade war operations in addition to regular exercises and intrusions?”