South Korean President Lee Myung-bak' s son will be summoned for questioning over allegations of irregularities in a land deal, prosecutors said Monday.

Last year, Lee's 34-year-old son Si-hyung and the presidential security service jointly bought 462 square meters of land in an affluent neighborhood in southern Seoul to build the president's retirement residence.

The plot was purchased in Si-hyung's name, a violation of South Korea's real estate law that prompted allegations of real estate speculation and tax evasion.

The junior Lee is also suspected of purchasing the land at a below-market price by letting the security service pay more.

The retirement home scandal drew public criticism, prodding Lee to scrap his plan, though prosecutors who initially probed the case acquitted everyone involved in the deal, including Si-hyung.

The case is being re-investigated by an independent counsel recommended by the opposition Democratic United Party. He can conduct a probe for up to 50 days.