Hyundai Motor and Kia Corp. will offer a software upgrade to 8.3 million U.S. vehicles in response to increasing thefts targeting vehicles without push-button ignitions and immobilizing anti-theft devices, U.S. auto safety regulators said.

Hyundai said it is "introducing a free anti-theft software upgrade to prevent the vehicles from starting during a method of theft popularized on TikTok and other social media channels."

The upgrade will cover 3.8 million Hyundai and 4.5 million Kia U.S. vehicles, the National Highway Traffic Safety Administration (NHTSA) said.

The agency said the effort is in response to a TikTok social media challenge that has spread nationwide "and has resulted in at least 14 reported crashes and eight fatalities."

Hyundai will also provide its customers with a window sticker alerting would-be thieves that the vehicle is equipped with anti-theft protection.

The software "updates the theft alarm software logic to extend the length of the alarm sound from 30 seconds to one minute and requires the key to be in the ignition switch to turn the vehicle on."

The initial Hyundai upgrade will cover more than 1 million 2017-2020 Elantra, 2015-2019 Sonata and 2020-2021 Venue model year vehicles. The software upgrade is scheduled to be available for remaining eligible affected vehicles by June.