Beijing's top official on Hong Kong affairs has called for unity in the SAR so that opportunities can be seized and development pursued, saying all sectors should contribute to the city's prosperity and stability.

Xia Baolong, the director of the Hong Kong and Macau Affairs Office, conveyed the message in a read-out at an event on Wednesday marking the 10th anniversary of think tank Our Hong Kong Foundation.

He also said One Country, Two Systems has entered a new phase with the city having bright prospects.

At the same event, Chief Executive John Lee said his administration will bring together all sectors in Hong Kong.

"The SAR government will do its best to unite society. We will encourage all sectors to proactively recognise, respond to and seek changes, while focussing on pursuing economic growth, seeking development and looking for breakthroughs," Lee said.

Bernard Chan, the foundation's chairman, pledged to strengthen connections with the international community.

"We must leverage our unique One Country, Two Systems framework, while reaffirming our status as an international city. We aim to expand collaborations with various stakeholders to unite Hong Kong's people and foster broader support," Chan said.

Liaison office chief Zheng Yanxiong, for his part, said Hong Kong desperately needs think tanks to further contribute their wisdom as the SAR moves from stability to prosperity.