Airport security personnel stand guard as travelers walk past protesters holding a sit-in rally at the departure gate of the Hong Kong International Airport in Hong Kong, Aug. 13, 2019.
Airport security personnel stand guard as travelers walk past protesters holding a sit-in rally at the departure gate of the Hong Kong International Airport in Hong Kong, Aug. 13, 2019.

 Suzanne Sataline contributed to this report from Hong Kong.

All departing flights from Hong Kong's international airport have been cancelled for a second straight day Tuesday after pro-democracy demonstrators once again took over the facility's main terminal.

The decision by the airport authority came just minutes after it suspended all passenger check-in services after protesters blocked passengers from entering their departure gates, and advised the general public not to come to the airport.  

The departure board shows all flights leaving Hong Kong canceled, Aug. 12, 2019.

The airport was already struggling to return to normal after reopening a day after hundreds of flights in and out of the airport were cancelled by a similar sit-in demonstration.  Some angry travelers anxious to leave Hong Kong got into heated arguments with protesters as Tuesday's demonstrations escalated, with some managing to push their way through the protest lines to catch their flights.  

The unprecedented shutdown of one of the world's busiest airports was an extension of the street protests that have gripped the Chinese territory for more than two months. Dozens of protesters were injured Monday after riot police fired tear tear gas and non-lethal ammunition after the protesters blocked roads and defied police orders to disperse.

Anti-extradition bill protesters wave flags with Chinese calligraphy that reads "Liberate Hong Kong, the revolution of our times," at a mass demonstration at Hong Kong International Airport, in Hong Kong, China, Aug. 12, 2019.

United Nations human rights chief Michelle Bachelet has issued a statement calling on Hong Kong authorities to exercise restraint and to investigate incidents involving tear gas fired at the protesters.

The government counted 54 people injured, including two who were hospitalized in serious condition Monday and 28 who were listed as stable, according to the Hospital Authority.

The protests began as a quest to stop a bill that would have allowed Hong Kong to send criminal suspects elsewhere, including mainland China.  Demonstrators are now demanding the right to directly vote for their next leader in a free and fair vote, and an independent inquiry into alleged police brutality.

Carrie Lam, Hong Kong's embattled leader, defended the police's actions during a press conference Tuesday, saying they had to make "on-the-spot decisions" under "extremely difficult circumstances."  Lam said she would address the protesters' demands "after the violence has been stopped and the chaotic situation that now we are seeing could subside."

Authorities in Beijing Monday termed the protests "terrorism."