Prime Minister Theresa May was in a meeting in Shanghai when a minivan ploughed into pedestrians in the city.
Mrs May was in China's commercial centre on the final leg of her three-day trip to the country when the incident happened.
The minivan veered onto a pavement and burst into flames, leaving 18 people needing hospital treatment, three of whom were said to be seriously injured.
It was later reported that Shanghai police were treating the crash as an accident, and not an attack.
It happened near People's Park, in the heart of the Chinese financial hub, at about 9.15am local time.
Mrs May was approximately four miles away at the Xingguo Hotel in the centre of the city at the time of the incident, at a meeting with Shanghai mayor Ying Yong.
It is understood that she was not made aware of what was happening at the time.
A British official travelling with the PM later said that Downing Street was aware of reports of the incident but had nothing further to say.
There was no indication that the incident had disrupted Mrs May's visit.
She is due to address business leaders in the city on Friday before heading back to the UK.