HONG KONG (REUTERS) - The union representing FedEx pilots has called on the US package delivery company to suspend its operations in Hong Kong after some of its members were subject to "extremely difficult conditions" in government-mandated quarantine aimed at tamping down the spread of the coronavirus.

The Air Line Pilots Association International (Alpa) said on Tuesday (July 28) that three FedEx pilots infected with the coronavirus were forced into mandated hospital facilities for up to 10 days in Hong Kong. Those pilots were asymptomatic.

Several other pilots who tested negative, but had been in contact with individuals who tested positive, were put in government camps "under extremely difficult conditions", the world's largest pilots' union said.

"Not only do these situations pose unacceptable risks to our pilots' safety and wellbeing, but they also create added stress and distraction for flight operations," said Mr Dave Chase, chairman of FedEx Alpa Master Executive Council.

In a statement, FedEx said the company was fully engaged with government authorities to support its crew members in situations that required medical treatment or self-isolation in Hong Kong.

The statement comes as Hong Kong implements tightened testing and quarantine arrangements for sea and air crew entering the Asian financial hub starting from Wednesday.

Before arriving, crew must test negative for Covid-19 within 48 hours of boarding. On arrival, they will be tested again and must self isolate without going into the community, the government said.

There have been numerous instances of aircrew flouting quarantine rules, including a FedEx pilot who flew from Boston to Hong Kong.

On July 26, one Twitter user based in Hong Kong posted that he had met the pilot on the city's historic Peak tram as he awaited his test results.

"You are not going to believe this! An American guy got on the tram and started chatting... Said he won't get results for two days - AND HE'S ON THE PEAK TRAM," the Twitter user posted.

After arriving in Hong Kong, crew have not been given clear guidelines as to what they can or cannot do while awaiting their test results, said one pilot who declined to be named because of corporate policy.

Authorities in the former British colony have warned that the city faces a critical period to contain the virus. Strict new measures that ban restaurant dining and restrict gatherings to two people also come into effect on Wednesday.

Hong Kong reported 106 new Covid-19 cases on Tuesday, including 98 that were locally transmitted.