SINGAPORE - A unit of Singtel has acquired two advertising technology firms for US$359 million (S$448.6 million) to strengthen its position as a mobile advertising company.

Amobee paid US$209 million excluding debt for Adconion and US$150 million for Kontera, SingTel said in a statement on Wednesday.

Its war chest comes from the $2 billion that Singtel last year earmarked for investment in the digital business.

Collectively, the acquisitions are SingTel's largest to date. In 2012, it paid US$321 million for Amobee.

These companies will let Amobee, which offers advertising in phones via SMS or text messages, to expand its digital mobile advertising offerings to email and social and video networks. They will also let brands offer personalised and targeted advertisements.

Amobee chairman Allen Lew said that with greater use of smartphones, many people are using the phone as their first device to access the internet.

"Customer preference and behaviour will change when people move to mobile Internet. The acquisitions will let us scale globally as well as track the customer behaviour for our advertising customers," said Mr Lew who is also SingTel's chief executive for Group Digital Life.

Amobee's revenue last year was US$100 million but it is not profitable yet. Mr Lew said The acquisitions will let Amobee reach new customers and markets so that it can accelerate its growth and reach profitability quickly.