Newspaper Korea JoongAng Daily are reporting HMG took the decision during the second half of 2020.
It also claims that while new diesel engine development has ceased, HMG will continue to update its existing 'R', 'U' and 'Smartstream D' series engines for current models.
That includes the 3.0-litre inline-six turbo-diesel mill found under the bonnet of the new Genesis GV80 (below), and widely slated to be used by Hyundai and Kia's upcoming dual-cab utes.
In Australia, both Hyundai and Kia use either engine family across their passenger, SUV and commercial vehicle ranges.
Industry insiders also told JoongAng Daily new petrol engine development is safe for now, as it plays a critical role in hybrid and plug-in hybrid vehicles.
The news brings the Hyundai group in line with other global car manufacturers, who have begun to phase out diesel engines.
In 2017, Volvo confirmed that it would no longer produce diesel engines, with the brand's Australian arm announcing in late 2020 that diesel engines would be phased out entirely from the local range by July 2021.
HMG is fast moving into the electric vehicle space, having debuted its new 'E-GMP' electric vehicle architecture.
The brand claims it will underpin a 23-strong electric vehicle range by 2025, and is targeting 10 per cent market share of the global EV market by 2040.