Hong Kong(CNN) China's President Xi Jinping underlined his commitment to "one country, two systems" as he arrived in Hong Kong to mark two decades of Chinese rule in the former British territory.

"For the past 20 years, Hong Kong has always had the strong backing of the central government," Xi said Thursday as he addressed crowds at the city's airport.

It's Xi's first visit as Chinese leader to the special administrative region. From the tarmac, he encouraged Hong Kongers to "look forward to the future, making sure 'one country, two systems' can work smoothly and continue," referring to the principle by which Hong Kong retains limited autonomy and freedoms.

Xi said the 20th anniversary of the city's handover from the United Kingdom to China on July 1 is a huge event "for the country, and for Hong Kong."

China's President Xi Jinping and his wife, Peng Liyuan, arrive in Hong Kong on June 29.

Protesters detained

Xi's first day in Hong Kong was a peaceful one, as predicted protests did not pan out. What rallies there were around town were mostly patriotic ones welcoming the Chinese President with songs and flags.

Huge banners were strung over the highway Xi took to the city, welcoming him for his "official inspection" and celebrating "20 years of Hong Kong's return to the motherland."

As Xi arrived at Hong Kong's Government House Thursday evening, to dine with Chief Executive CY Leung and other dignitaries, groups of pro-China demonstrators thronged a nearby road, wearing red caps and waving the country's flag.

Activist Joshua Wong was arrested Wednesday in Hong Kong's Golden Bauhinia Square ahead of the 20th anniversary of the city's handover to China.

A major reason for the relative calm is that former "Umbrella Movement" leaders Joshua Wong, Nathan Law and other activists are languishing in police custody after they were arrested Wednesday night.

The pair were arrested with two dozen others after they occupied Golden Bauhinia Square, where an official flag raising ceremony attended by Xi will take place later this week.

As of Friday morning, all 26 protesters had been released from custody, a spokesperson for the activists confirmed.

China's President Xi Jinping, center, waits to meet with Hong Kong's chief executive Leung Chun-ying at a hotel in Hong Kong on June 29.

Huge security operation

Much of Wan Chai, a bustling business district in the city center where Xi will stay, is on partial lockdown, with 300, 2-ton barricades erected on roads around the Hong Kong Convention and Exhibition Center. The venue will host many events marking the city's handover from the UK to China.

Around 11,000 of the city's 29,000 police officers have been drafted to take part in security arrangements for Xi's visit, according to the South China Morning Post.

During a visit last year by Zhang Dejiang, the third-highest ranked Chinese leader, sidewalks were glued down in key areas to prevent protesters from breaking them up and using them as missiles.

Local media reported this week that police were under instructions to prevent banners and signs that might "embarrass" Xi from appearing within his eyesight.

Barriers were also briefly erected around a statue of Queen Victoria in a central Hong Kong park named for the long-reigning British monarch, but they were removed after complaints.

Events and celebrations

While in Hong Kong, Xi will spend little time anywhere near the public.

However, shortly after she arrived on Thursday, Xi's wife, Peng Liyuan, made a visit to a Hong Kong kindergarten, where she watched student performances and talked to the children, according to a Hong Kong government press release.

Peng was presented by the students with a fan covered in hand-painted pandas. She later joined Xi for dinner with Leung and incoming Hong Kong Chief Executive Carrie Lam at Government House.

On Friday, Xi is expected to visit a People's Liberation Army base to inspect the troops. Until recently, China's military has kept a low profile in Hong Kong but this looks to be changing.

Beijing is also sending its prized aircraft carrier to Hong Kong for the celebrations -- a show of military might not seen since it made the territory a special administrative region in 1997.

Chinese President Xi Jinping's motorcade arrives at Government House in Hong Kong's Central district on June 29.

An elaborate celebratory gala will be held Friday evening at the Hong Kong Convention and Exhibition Centre, attended by Xi, Leung, Lam and other dignitaries.

Protests are expected outside the event, and at a separate rally by pro-Hong Kong independence activists, who have called for their supporters to gather together and "crush Chinese colonialism."

Xi will leave the city on Saturday after swearing in Lam and attending a flag-raising ceremony to mark the 20 years since China assumed sovereignty over Hong Kong.

Attention will then turn to the annual July 1 pro-democracy march, which organizers expect to attract hundreds of thousands of people.