SEOUL, April 10 (Reuters) - KB Financial Group Inc has signed a share purchase agreement to buy a 100% stake in U.S. Prudential Financial Inc's South Korean unit for 2.3 trillion won ($1.89 billion), the group said in a filing on Friday.

The deal marks the No.1 U.S. life insurer's exit from the South Korean market after 30 years.

Prudential had hired Goldman Sachs to review a possible sale of the unit, a South Korean newspaper reported in November. ($1 = 1,217.1700 won) (Reporting by Heekyong Yang and Joyce Lee; Editing by Himani Sarkar)