Ride-hailing service Grab has removed a driver from its platform over allegations that he flashed his privates while ferrying a passenger to a mall in Petaling Jaya.

"We have removed the driver off our platform. We are also getting in touch with the passenger and assisting her further," Grab said on Twitter.

It also told the passenger it is looking into the matter and investigating the driver.

"Such action is not tolerated on our platform and we are terribly sorry for this horrible experience," it said.

The passenger had before that taken to Twitter to say that she contacted Grab immediately and was advised to lodge a police report.

The passenger, whose name and Twitter handle is withheld for security reasons, said she was afraid to do so as the driver knew her address and phone number, and could harm her and her family.

She used the Grabhitch service to go to Sunway Pyramid on Saturday.

She noticed that the driver had his penis out just as they were entering a highway.

"As we're getting on the highway, I look over and this dude had his d*** out. I was like, 'WTF is happening?' At this point I'm panicking.

"Thank God I had my keys with me. I was holding them in my hands and I just ignored him. I wanted to get out of the car so badly," she wrote on Twitter.

She said she felt something was amiss when she noticed the driver was dressed in shorts and a singlet, but figured he might be dressed so because he was a Grabhitch and not Grabcar driver.

Grabhitch is a service where users can hitch a ride with private drivers who are going the same way, for a small fee.

Grabcar is a service where private drivers ferry paying passengers to any destination required.

In a statement later today, Jaygan Fu, Country Head of Grab Malaysia said passenger safety is of utmost concern as the service exists to address this safety issue and driver welfare.

"We sincerely regret the terrible experience she had and we are glad that she reached out to us. Our team is in contact with her and and we have removed the driver from our platform," he said.

He urged passengers to "exercise their right to safe transport" and to contact Grab immediately if they feel unsafe, so the firm can intervene.

"Their feedback will help us to continuously improve our services and quality of drivers," he said.

The government is in the process of legalising ride-hailing services like Grab and Uber, to much objection from the taxi industry.

Some from the taxi industry caution it is unsafe for passengers, especially for young women who prefer ride-hailing services, as there is hardly any vetting of drivers.

Ride-hailing services are generally perceived to be safer than conventional taxis as passengers can send alerts to friends and family, giving driver and journey details.

Drivers are also rated by each passenger, with average ratings affecting their earnings.

Editor's note: Embedded Twitter posts have been removed from the story to protect the victim's identity. We regret the error.