An outage on the Tesla app left some drivers unable to access their car, reports suggest.

Owners reported on social media seeing an error message on the mobile app that was preventing them from connecting to their vehicles.

The Tesla app is used as a key by drivers to unlock and start their cars and, while it is not the only way to access Tesla cars, many drivers rely solely upon it.

About 500 users reported an error on the app at around 9.40pm on Friday, according to the outage tracking site DownDetector. Five hours later, there were just over 60 reports of an error.

"I'm stuck an hour away from home because I normally use my phone to start car," one owner tweeted.

The BBC reports that Tesla chief executive Elon Musk personally responded to one complaint from a driver in South Korea, saying on Twitter: "Checking." Musk later said the app was coming back online.

"Apologies, we will take measures to ensure this doesn't happen again," he tweeted. 

Automotive expert Professor David Bailey from the Birmingham Business School, who drives a Tesla, experienced the outage on Friday.

"To some extent, Tesla is a bit of a victim of its own success," he told the BBC. "It encourages its customers to use the cutting-edge technology it creates and sometimes that will go wrong.

"Although of course you can use a key to open the car too, the natural instinct of many Tesla drivers, who are buying one of the most high-tech models in the market, is to rely on the technology."