The biggest rally is expected to take place on Sunday on the main island.
The Hong Kong protests started as a peaceful rebuke of the government in April but have evolved into a direct challenge to Chinese rule over this former British colony.
Hurt by the plunge in US-Chinese trade, growth was already declining in Hong Kong this year before anti-government protests erupted over a proposed extradition law and other grievances.
The chair of the influential Foreign Affairs Committee has suggested giving Hong Kong citizens full nationality as a show of support, saying it should have happened in 1997.
China's ambassador to the United Kingdom said Beijing would use its power to quell Hong Kong protests if the situation deteriorates further.
Flights resumed amid heightened security at Hong Kong airport. By nightfall, police and protesters were again facing off on the streets, with riot officers shooting tear gas almost immediately.
Investor anxiety has been fed by President Donald Trump's threat of new US tariff hikes on Chinese goods, protests in Hong Kong and weaker-than-expected data from India, Argentina and Singapore.
The airport, one of the world's busiest, blamed demonstrators for halting flights on Monday, but the exact trigger for the closure was not clear as protesters occupying the arrivals hall for the past five days have been peaceful.
Cathay became embroiled in Hong Kong's protests when China's civil aviation regulator demanded the airline suspend personnel who engaged in or supported illegal protests in Hong Kong from staffing flights into its airspace.
Police and protesters clash as yet another day of protest marches in Hong Kong turned into a confrontation between police and activists.
Hong Kong is facing an economic crisis worse than either the 2003 SARS outbreak that paralysed the city or the 2008 financial crisis, leader Carrie Lam said.
As a three-day sit-in protest at the airport continues, several hundred families are taking to the streets to show support for anti-government demonstrations that are now in their third month.
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