Hyundai Motor Co unveiled two new sedans built for its home South Korean market on Thursday, an unusual step designed to fend off surging imports from the likes of BMW and Audi.

The move on the eve of the Busan Motor Show reveals Hyundai's jitters about imports from Europe and the US, which have soared in popularity since free trade deals cut tariffs on foreign-made vehicles in recent years.

Foreign carmakers expect to more than double their South Korean market share to 20 percent by 2016, compared with 2012 when tariffs on US-made imports started to unwind.

Import duties on European-made vehicles began to fall from 2011.

Hyundai's new large car, the AG, and a diesel version of the Grandeur (Azera) sedan were unveiled ahead of the Busan Motor Show which kicks off on Friday.

The AG, slotted between the Grandeur and Genesis large sedans, will be priced from about 45 million won ($44,100) and will go on sale late this year, Hyundai said.

The Grandeur Diesel, which features a modified version of the 2.2-liter engine used in the Santa Fe, Hyundai's mid-sized sport utility vehicle, will hit domestic showrooms next month.

It is Hyundai's first large diesel car built for the domestic market, and is aimed directly at a segment where imported cars are making strong gains.

Diesel cars accounted for 62 percent of total imported cars sold in South Korea last year, up from 25 percent in 2010.