HONG KONG — Hong Kong International Airport says it will restart flights beginning at 6 a.m. on Aug. 13 after it completely shut down operations on Monday when thousands of pro-democracy demonstrators occupied its main terminal.

All flights Monday that had not completed check-in procedures by afternoon were cancelled, as were arriving flights that had not yet taken off.

Hong Kong International Airport is  one of the world’s busiest airports.

Airport staff advised passengers to leave the airport for their own safety, but traffic outside was at a near standstill, and public transportation was clogged. Some passengers and departing protesters opted to walk.

Hong Kong has experienced more than two months of mass protests calling for democratic reforms and an independent inquiry into police conduct. The city, a former British colony, was returned to China in 1997 under the “one country, two systems” principle.

The chief executive of Hong Kong’s Cathay Pacific Airways has said there will be “disciplinary consequences” for employees involved in “illegal protests,” as the airline joins a slate of businesses that have appeased and apologized to China in recent days over political flaps.

Rupert Hogg’s comments Monday came just hours before the Hong Kong airport announced it was temporarily shutting down.

Hogg warned in an internal memo to employees that the company has a “zero tolerance approach to illegal activities,” referring apparently to protests unapproved by the police force.

Companies from luxury fashion brands to bubble tea shops have been under pressure to distance themselves from protesters and declare their support for the ruling Communist Party’s position on Hong Kong.

Meanwhile Hong Kong police have defended their tactics and use of force against protesters during another weekend of violent clashes, including using tear gas inside a train station, deploying officers disguised as protesters and allegedly shooting at demonstrators at close range with pepper-spray pellets.

The police attempted to fend off criticism Monday about widely shared videos from Sunday night’s clashes.

Deputy Commissioner Tang Ping-keung acknowledged that police use decoy officers in some operations but would not go into details.

“Our decoy officers do not take part in any unlawful activities,” Tang insisted.

Police confirmed that officers fired one shot of tear gas into a train station Sunday, saying it was necessary to disperse violent protesters. Addressing criticism of riot police firing pepper spray pellets at close range, officials said the weapon was not lethal but they would review the incident.