China showcased state-of-the-art ballistic missiles at the country's largest-scale military parade to mark the 70th anniversary of Communist rule on Tuesday, with mounting political unrest in Hong Kong testing President Xi Jinping's grip on power.

Against a backdrop of months-long anti-China protests in Hong Kong and a tit-for-tat trade dispute with the United States, the leadership under Xi aimed to use the military parade to boost national prestige, according to diplomatic experts.

In his keynote speech ahead of the parade, Xi pledged to attain "the great rejuvenation of the Chinese nation" while calling for unity of all citizens, in a sign that he has no intention to easily make concessions to Hong Kong protesters.

"We must support the principle of peaceful reunification and one country, two systems," Xi said, adding, "We will maintain long-term prosperity and stability of Hong Kong."

"Over the past 70 years, people of all nationalities in the country have worked hard together to achieve the great achievements that have drawn attention from the world," Xi said. "No power can stop the progress of the Chinese people and the Chinese nation."

Since June, there have been protests almost every weekend in Hong Kong, many turning violent, which were initially triggered by a now-abandoned extradition bill that would have allowed Hong Kong citizens to be sent to mainland China for trial.

Recently, the protesters have been making five demands, including electoral reforms and an independent inquiry into alleged police brutality during protests, but mainland China has shown little sign of accepting them.

Hong Kong citizens held protests across the territory Tuesday, with police shooting an 18-year-old protester, reportedly a high school student, in what marks the first case of its kind since the protests began in June.

The male student was hospitalized in critical condition after being shot in the chest in a clash with police, local media said.

The huge military parade took place in China's capital amid fears that the Chinese leadership may violently intervene to end such protests, as it did during the military crackdown on a pro-democracy movement at Beijing's Tiananmen Square in 1989.

Under the framework of "one country, two systems," Hong Kong was promised it would enjoy the rights and freedom of a semi-autonomous region following the former British colony's return to Chinese rule in 1997.

But critics say the Communist Party has been trying to gradually bolster its clout in the territory before 2047, when the 50-year transition agreement expires.

On Tuesday, Beijing-backed Hong Kong leader Carrie Lam participated in a ceremony in the territory to celebrate the 70th anniversary of the founding of the People's Republic of China.

As the nation's economy has become the world's second-largest after the United States, Xi, who heads the country's military, has also committed to stepping up efforts to give the military "world-class" status by the mid-21st century.

Among the most closely watched military hardware in the parade were the Dongfeng 41, a nuclear-capable intercontinental ballistic missile believed capable of hitting almost anywhere in the United States, and the Dongfeng 17 hypersonic missile.

Former Chinese presidents Jiang Zemin and Hu Jintao also attended the National Day ceremony, which Xi's leadership has viewed as this year's most important event.

Streets in the city were cleaned overnight, security was tight and traffic was conspicuously thin on Tuesday morning on roads that had been mostly shut down the previous night to facilitate preparations.

Around 15,000 military personnel, more than 160 aircraft and 580 pieces of equipment featured in the parade, which passed along Chang'an Avenue, the capital's major thoroughfare, and through Tiananmen Square.

National Day is a key holiday in China's political calendar. On Oct. 1, 1949, communist leader Mao Zedong declared the founding of the People's Republic of China after defeating Chiang Kai-shek's Nationalist army and finally ridding the nation of foreign forces.

On the occasion of the founding anniversary, U.S. President Donald Trump, Russian President Vladimir Putin, North Korean leader Kim Jong Un and other foreign leaders have sent congratulatory messages to Xi, Chinese media reported.

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