WPP said its unit JWT had agreed to buy a majority stake in South Korean digital agency Post Visual which counts Nike, eBay and Google among its clients.It is the latest in a long string of acquisitive deals announced by the advertising giant this month. Seoul-based Post Visual was founded in 2000 employs 60 people and made revenues of 4.8bn South Korean won(£2.8m) in 2012.WPP, which already employs 1,400 people in South Korea, said: "This investment marks a further step towards WPP's declared goal of developing its networks in fast-growth and important markets and sectors."WPP, which is led by Sir Martin Sorrell, didn't disclose how much JWT had paid for the stake.Shares in the advertising group were down 0.94% at 1157p at 11:51 on Friday. TB