Japanese telecom giant SoftBank will invest $250 million in Southeast Asian mobile taxi booking app GrabTaxi, the two firms said Thursday, as rivalry in the region between US-based Uber and homegrown rivals increases.
In a statement, the pair said the deal will make Softbank the biggest investor in the Malaysia-based startup.
"This new round of funding will help drive our mission of revolutionising and improving the way Southeast Asians commute more aggressively than ever before," Anthony Tan, GrabTaxi's chief executive and founder, said in the statement.
GrabTaxi, which is also backed by Singapore state investment firm Temasek Holdings, operates in 17 cities across Singapore, Malaysia, Thailand, Vietnam, Indonesia and the Philippines.
Its app employs smartphone and satellite technology to match customers with registered taxis close to their location.
According to GrabTaxi, the service has the largest network of its kind in Southeast Asia, with more than 500,000 active users and 2.5 million app downloads to date. It currently has a total of 60,000 taxi drivers in its network, up fourfold from 2013, the firm said.
With the SoftBank investment, GrabTaxi has raised $340 million in the past 14 months, it added. The company was founded in 2012 by Tan, the scion of one of Malaysia's richest families.  
The fresh investment comes as Uber attempts to gain a foothold in the region despite multiple regulatory tangles and already fierce competition.
Within Southeast Asia, Uber operates in the same six markets as GrabTaxi, after entering Singapore last year. It does not release operational statistics.
Malaysian and Indonesian authorities have said Uber services that utilise private vehicles are illegal, while Thai authorities last week indicated that they are also banning the service.
Other major taxi apps in Southeast Asia include Indonesia's Blue Bird, regional player EasyTaxi, backed by German startup incubator Rocket Internet, as well as London-based Hailo which operates in Singapore.
The apps are seen as revolutionising the taxi industry, which has long been plagued by inefficient cartels and price-gouging drivers.
Nikesh Arora, vice chairman of SoftBank, said it would support "GrabTaxi's further expansion in the region".
SoftBank in October announced a $627 million investment in Indian online marketplace Snapdeal. It also said in October it was jointly investing $210 million in ANI Technologies, better known as the taxi booking app Ola Cabs.