SoftBank Corp. has invested $250 million in GrabTaxi Holdings Pte. as the cab-booking service fends off competition from Uber Technologies Inc. in Southeast Asia.

SoftBank Internet and Media Inc., a unit of the Japanese company, will become the largest investor in GrabTaxi, Anthony Tan, who set up the mobile phone application in 2012, said in an interview in Bangkok on Wednesday without providing stake details.

SoftBank confirmed the GrabTaxi investment on its website Thursday.