Cathay Pacific has warned staff they could be fired if they “support or participate in illegal protests” in Hong Kong, as pressure from Beijing intensifies.

The warning was emailed to staff by chief executive Rupert Hogg on Monday.

On Friday, China ordered the airline to suspend workers who support pro-democracy protests in the territory.

Cathay fired two employees and suspended one pilot over the weekend in response to the order.

Also on Monday, Hong Kong International Airport cancelled more than 100 departing flights, as anti-government protests in its main terminal continued for a fourth day.

Cathay Pacific is now subject to new regulations announced last week by Beijing’s aviation regulator, the Civil Aviation Administration of China (CAAC), which came into effect on Sunday.

These require it to submit lists of staff working on flights going to the mainland or through its airspace.

Any staff member accused of involvement in “illegal protests” is banned from working on those flights. Authorities have warned planes could be prevented from landing if they do not comply.

The regulator has also demanded a report from Cathay by 15 August on planned measures to “strengthen internal control and improve flight safety and security”.