In the January-October period, the number of diesel vehicle imports came to 6,740, down 65.1 per cent from the same period last year, according to the data from the Korea Automobile Importers & Distributors Association (KAIDA).

In October alone, the number plummeted 58.7 per cent on-year to 643. The January-October figure accounted for 3.1 per cent of all imported vehicles, marking the smallest market share since 2004, reports Yonhap news agency.

The local market share of diesel imports had peaked at 69 percent in 2015 after breaching the 20 percent and 30 percent marks in 2009 and 2011, respectively, according to KAIDA.

The sharp decline in the number of diesel imports was partly attributed to the so-called Dieselgate, where German carmaker Volkswagen AG was found in 2015 to have passed emissions tests by using "defeat devices."

"Sales of diesel cars are slowing more rapidly in South Korea than in other countries due to the fast electrification of vehicles here," a local market watcher said.

Earlier data showed the number of new gasoline and diesel vehicles registered in South Korea plunged 19.6 percent and 56.7 percent on-year, respectively, in the first nine months of the year.

Those of electric vehicles slipped only 7.9 percent, while the number of new hybrid vehicles jumped 27.6 percent on-year over the cited period, the data showed.