Seoul_GangnamDistrict
Part of Gangnam area is seen down the Han River (L) in Seoul on Oct. 2, 2012. Gangnam is the most upmarket neighbourhood in the South Korean capital. Known as Seoul's "Beverly Hills", its streets are lined with designer-brand shops and trendy bars and restaurants. Reuters/Lee Jae-Won

(Reuters) - Hyundai Motor and two listed affiliates did not seek board clearance for the size of their record $10 billion (6.14 billion British pound) bid for a plot of land in Seoul, more than triple its appraised value, four board members of the companies told Reuters.

Thursday's winning bid for the land sent shares in Hyundai Motor, Kia Motors and Hyundai Mobis plunging, wiping out $8 billion in shareholder value, and sparked howls of protest from investors, rekindling worries about corporate governance at South Korea's conglomerates, or chaebol.

While boards of the three firms discussed and approved bidding for the plot in the capital's high-end Gangnam district to house a headquarters complex, hotel and automotive theme park, the bid price was not shared with directors as it was deemed to be confidential, three of the directors said.

The Hyundai Motor and Kia Motors boards unanimously approved making a bid for the KEPCO land, two directors said.

"The price was top secret, so it was not something we discussed at the meeting," said one, declining to be identified given the sensitivity of the matter. "The intangible benefits go beyond the appraisal price of the land."

Another director at one of the companies said its board heard and discussed information about the appraisal price of the KEPCO land and the value of nearby buildings