Romania's French Open champion managed just a set against Tunisia's Ons Jabeur before leaving the court at the National Tennis Center in China's capital.

"There is a pain," said Halep, who had also struggled with the injury at last week's Women's Tennis Association (WTA) event, the Wuhan Open, as she lost her opening match against Dominika Cibulkova.

"I couldn't move properly, so that's why I stopped.

"I don't know exactly what it is.

"I will go home.

"I will have an MRI and I will see.

"I'm just worried now - I feel sad that I couldn't finish."

The retirement win is Jabeur's second career "victory" against a top 10 player.

"I didn't want the match to end like this - I wanted a real battle," Jabeur said.

It was the second match to end by retirement in Beijing today, as Daria Kasatkina pulled out with gastrointestinal illness against Germany's Laura Siegemund when trailing 6-3, 4-2.

Wimbledon champion Angelique Kerber of Germany dropped just four games in defeating France's Kristina Mladenovic.

Kerber, seeded third, made an emphatic start to her campaign, surrendering just four games.

She needed just 71 minutes to pull off a 6-2, 6-2 victory and move safely through to the second round at the final WTA Premier mandatory event of the season.

A marathon opening day at the China Open came to an end as the clock approached midnight yesterday, as number 10 seed Julia Goerges of Germany overcame Britain's number one Johanna Konta 6-2, 4-6, 6-3 in a match lasting two hours and 15 minutes.

Action will continue tomorrow, including day one of the men's event.