HONG KONG - Abu Dhabi sovereign investor Mubadala Investment Company this week formally opened its Beijing office amid warming ties between the world's second-largest economy and the Gulf Arab states, five people with knowledge of the matter said.

Mubadala Investment Company is the second-biggest state fund in Abu Dhabi, the capital of the United Arab Emirates, after Abu Dhabi Investment Authority (ADIA).

While economic ties between China and the Gulf states remain anchored by energy interests, bilateral relations have expanded under the region's infrastructure, technology and financial push and amid Sino-U.S. geopolitical tensions.

Mubadala entered China a few years ago, but had to delay its office opening ceremony due to restrictions imposed during the COVID-19 pandemic, said one source.

Mubadala's Beijing-based team, about 10-strong, focuses on direct investments and fund investments in the country, said a second source. Its China portfolio includes JD Industrials, Hasten Biopharmaceutic and online fashion retailer SHEIN.

All the sources declined to be named as they were not authorised to speak to the media.

Mubadala's Chief Executive Khaldoon Al Mubarak, deputy CEO Waleed Al Mokarrab Al Muhairi attended Tuesday's event, sources said.

"Our Asia investment strategy has been in place for several years, with promising growth prospects throughout the region," said a Mubadala spokesperson when contacted by Reuters about its China investment plans.

The firm did not comment on the Beijing event.

Prominent Chinese private equity investors including Lei Zhang, the founder of private equity fund Hillhouse, and Neil Shen, founder and managing partner of venture capital firm HongShan, attended the event, said the five sources.

Weijian Shan, executive chairman and co-founder of Hong Kong-based private equity firm PAG; and David Liu, former KKR head of Greater China and founder of China-focused buyout fund DCP Capital, were also among the guests, they said.

HongShan, DCP and PAG declined to comment. Hillhouse did not immediately respond to a request for comment.

(Reporting by Julie Zhu and Kane Wu in Hong Kong; additional reporting by Hadeel Al Sayegh in Dubai; Editing by Sumeet Chatterjee)