Hong Kong's Airport Authority said normal flight operations would resume on Thursday after pro-democracy protests forced the cancellation of nearly 1,000 flights this week, while the city braced for more mass protests through the weekend.

China reiterated on Wednesday that Hong Kong's protest movement was "near terrorism" and more street clashes followed ugly and chaotic scenes at the airport on Tuesday, when protesters set upon two men they suspected of being government sympathizers.

Police and protesters faced off again on the streets of the financial hub overnight, with riot officers quickly firing tear gas as their response to demonstrators toughens .

The Hong Kong and Macao Affairs Office, in a statement issued on Wednesday, also strongly condemned attacks against a reporter from one of China's largest government-backed newspapers and a traveller at the airport by what it said were violent protesters.

People run away from tear gas fired by police to disperse protesters in Hong Kong's Sham Shui Po neighbourhood Wednesday night, as Beijing condemns demonstrators. (Tyrone Siu/Reuters)

By nightfall, police and protesters were again clashing on the streets, with riot officers shooting tear gas almost immediately as their response to demonstrators toughens. They fired tear gas at a group of pro-democracy protesters rallying outside a police station in the crowded Sham Shui Po neighborhood.

The protesters had gathered to burn "hell money" and incense as a way to show their opposition to the police during the month-long Hungry Ghost Festival, when offerings are made to ward off spirits of ancestors.

Airport reopened after clashes

Ten weeks of increasingly violent clashes between police and pro-democracy protesters, angered by a perceived erosion of freedoms, are posing one of the biggest challenges for Chinese President Xi Jinping since he came to power in 2012.

Protesters also apologized Wednesday that some of them had become "easily agitated and overreacted."

Hong Kong protesters offer an apology to the public over airport chaos - from a telegram group so it's unsigned and not official but it's how they've been communicating with journalists <a href="https://t.co/hDXDJwAWcu">pic.twitter.com/hDXDJwAWcu</a> —@erinhale

"It is not our intention to cause delays to your travels and we do not want to cause inconvenience to you," said an emailed statement from a group of protesters. "We ask for your understanding and forgiveness as young people in Hong Kong continue to fight for freedom and democracy."

Hong Kong's airport resumed operations on Wednesday after being forced to halt check-ins Monday and Tuesday, rescheduling hundreds of flights that had been disrupted over the past two days as protesters clashed with riot police.

Hong Kong's Airport Authority said it had obtained "an interim injunction to restrain persons from unlawfully and willfully obstructing or interfering" with airport operations. It said an area of the airport had been set aside for demonstrations, but no protests would be allowed outside the designated area.

Watch as protesters clash with police on Tuesday inside Hong Kong's airport:

Police and protesters clashed at Hong Kong's international airport Tuesday evening after flights were disrupted for a second day. 0:59

Security at the airport was stricter than usual with several entrances closed, police patrolling and staff checking traveller identification; the airport authority said it would only allow entry for passengers with a boarding pass valid for the next 24 hours.

Some protesters expressed remorse for the clashes overnight. One 22-year-old frontliner who identified himself as Pun said protesters needed to re-evaluate their strategy to continue with the fight.

"We are not trying to overthrow the government or cut ourselves off from China. But we fight for our rights; democracy was promised as part of 'one country, two systems.'"

A few dozen protesters remained at the airport early in the day while workers scrubbed it clean of blood and debris from overnight. Check-in counters reopened to queues of hundreds of weary travellers who had waited overnight for their flights.

Hong Kong police said they arrested five people over the past two days in the airport for unlawful assembly, assaulting police officers and possessing weapons, bringing the number arrested since the protests began in June to more than 600.

Paramilitary vehicles reportedly spotted across the border

The United States said it was "deeply concerned" after satellite photos collected Monday by a U.S. space technology company showed what appear to be armoured personnel carriers and other vehicles belonging to China's paramilitary People's Armed Police parked in a sports complex in the city of Shenzhen — located just across the border from Hong Kong.

The pictures collected by Maxar's WorldView imaging satellite, show vehicles sitting on and around the soccer stadium at the Shenzhen Bay Sports Center in what some have interpreted as a threat from Beijing to use increased force.

This satellite image captured on Monday by Maxar Technologies appears to show Chinese security force vehicles inside the Shenzhen Bay Sports Center in the southern Chinese city that borders Hong Kong. (Maxar Technologies via AP)

Chinese state media have said only that the exercises had been planned beforehand and were not directly related to the unrest in Hong Kong, although they came shortly after the central government in Beijing said the protests were beginning to show the "sprouts of terrorism."

The U.S. on Wednesday urged Hong Kong's government to respect freedom of speech and issued a travel advisory warning people to be cautious when visiting the city.

Meanwhile, in statement, French Foreign Minister Jean-Yves Le Drian called on Hong Kong authorities to renew talks with protesters to find a peaceful solution to the current crisis "and to put an end to the escalation of violence."

The Chinese city of Shenzhen is located across the border from Hong Kong. Paramilitary police were assembling in Shenzhen for exercises in what some saw as a threat to the pro-democracy protesters in Hong Kong. (CBC News)

Chinese state media on Wednesday called on Beijing to deal with protests in Hong Kong more decisively. A front-page commentary on the overseas edition of the Communist Party's official People's Daily newspaper said on Wednesday Hong Kong had reached a critical juncture.

"Using the sword of the law to stop violence and restore order is overwhelmingly the most important and urgent task for Hong Kong!" it said.

Demonstrators say they are fighting the erosion of the "one country, two systems" arrangement that enshrined some autonomy for Hong Kong after China took it back from Britain in 1997.

They are also demanding Hong Kong leader Carrie Lam step down and scrap proposed legislation under which some suspects could be sent to mainland China, where critics say they could face torture and unfair or politically charged trials.

"Extreme political ideas have found frequent expression in Hong Kong, with some even raising 'Hong Kong independence' slogans recently. Which means the 'one country, two systems' principle faces a new challenge," Chinese author Li Peiwen said.

Some 21 countries and regions have issued travel safety alerts, saying the protests have become more violent and unpredictable. Canada increased its travel advisory for Hong Kong due to the ongoing protests, advising travellers to exercise "a high degree of caution."