Having spent the night in Shenzhen, Xi crossed the border again by high-speed rail in the morning to preside over the inauguration and is expected to deliver a keynote speech.

Friday's celebrations began with a flag-raising ceremony at the city's Victoria Harbour, complete with a military flypast and a flotilla spraying plumes of water.

Buffeted by strong winds, a crowd including incoming chief executive Lee watched as goose-stepping soldiers released the Hong Kong and Chinese flags to the sound of the national anthem.

Xi was not present among the several hundred attendees at the flag-raising ceremony which also include outgoing leader Carrie Lam Cheng Yuet-ngor, and former leaders Leung Chun-ying and Donald Tsang.

At around 9.55am, Xi and his wife Peng got inside a vehicle at the terminus in West Kowloon and their motorcade headed to the Hong Kong Convention and Exhibition Centre to attend the anniversary celebrations and oversee the swearing-in of Lee’s cabinet.

At 10.10am, guests give a big round of applause as they entered the grand hall of the Hong Kong Convention and Exhibition Centre, along with incoming leader Lee and his wife.

After swearing in Lee as Hong Kong’s fifth chief executive, the state leader also sworn in principal officials, including the three top secretaries, their deputies, and 15 bureau ministers. The male ministers stand at the front, while the female ones are behind.

Lee then oversees the swearing-in of those in the Executive Council, which includes 21 principal officials and 16 non-official members.

Veteran politician Regina Ip Lau Suk-yee, a former security chief, has been picked as the new convenor of Exco, Lee’s de facto cabinet. Seven of the non-official members are new in the cabinet.

Xi is expected to return to the mainland at noon, ending his two-day visit.

Upon arriving by high-speed train on Thursday afternoon, the state leader said in a brief speech that "After the storms, Hong Kong has been reborn from the fire and emerged with robust vitality".