China-based artificial intelligence (AI) company SenseTime raised $620 million in a second funding round in just two months, giving it a valuation estimated at $4.5 billion and maintaining its position as the world’s most valuable AI start-up.

The company, which specialises in facial recognition technology, said the C+ funding round was led by Fidelity International, Hopu Capital, Silver Lake and Tiger Global. A number of previous investors, including Qualcomm Ventures, also participated.

The Beijing-based company’s total financing has hit more than $1.6 billion.

SenseTime said in a statement it will continue to invest in R&D and staff.

The three-year-old company said it was profitable in 2017 and has seen revenue grow 400 per cent annually since the start.

It recently signed a traffic monitoring deal with Shanghai Shentong Metro Group, the largest subway operator in China, and announced plans to set up a regional headquarters in the city of Chengdu to align with the country’s Belt and Road initiative to develop the western part of China. Last week it teamed up with Alibaba and Hong Kong Science & Technology Park to establish an AI lab in Hong Kong.