Japan's SoftBank said Wednesday it will buy US asset manager Fortress Investment Group for $3.3 billion, as it moves to hire experienced money managers before launching a major technology investment fund.

The mobile giant said it was paying $8.08 a share for New York-based Fortress, a 39 percent premium on its February 13 close price.

Fortress is a global investment firm with 1,100 employees and $70.1 billion in assets under management as of September last year, according to a joint statement.

SoftBank said the firm's top management would stay in place and it would continue to operate  independently under its umbrella.

"We look forward to benefiting from its leadership, broad-based expertise and world-class investment platform," said SoftBank chief executive Masayoshi Son.

Son was among the first business people to meet Donald Trump after his November election victory.

SoftBank's founder pledged to invest $50 billion in business and job-creation in the United States, winning praise from the then-president-elect.

Son later said the money would come from the $100 billion technology investment fund he is setting up with Saudi Arabia's sovereign wealth fund and other partners, a move announced in mid-October.

The Japanese billionaire plans to use the SoftBank Vision Fund to invest heavily in the "Internet of Things," artificial intelligence and robotics.

SoftBank, which is little known outside Japan, has gone on an acquisition spree over the years. It paid $22 billion for 80 percent of US mobile carrier Sprint in 2013 and more recently announced the $32-billion purchase of British iPhone chip designer ARM Holdings -- raising concerns about its debt-heavy balance sheet.

SoftBank shares rose 1.58 percent to close at 8,670 yen in Tokyo on Wednesday.

SoftBank has said it will put up about $25 billion for the Vision Fund over the next five years, while the Saudi public investment fund's contribution could reach $45 billion.

SoftBank is aiming to close the first round of investment in the Vision Fund by the end of this month, Bloomberg News reported, citing people familiar with the matter. 

US tech giants Apple and Qualcomm, as well as Oracle chairman Larry Ellison will invest $1.0 billion each in the fund, Bloomberg said.