BUENOS AIRES, Oct 4 (Reuters) - Argentina's fintech unicorn Uala will invest $150 million over the next 18 months to boost its digital banking business, mainly in Mexico and Colombia, its Chief Executive Pierpaolo Barbieri said in an interview with Reuters.

The fast-growing firm, which has a valuation of some $2.5 billion, is aiming to expand its user base at least fivefold to 25-30 million people in the next five years, from five million users currently around in Latin America.

"In the next 18 months alone we are going to invest $150 million more in growth," Barbieri, 35, said at the companies offices in Buenos Aires. "Most of those funds are going to be destined to push growth in Mexico and Colombia.

Uala bought Argentine digital banking company Wilobank this year and invested $80 million to operate in Colombia, after closing an investment round for $350 million in 2021 and acquiring Mexican bank ABC Capital.

"In a market context where others are cutting investment, we are expanding because we already have the capital," said Barbieri, adding the firm wanted to expand its financial offerings into debit cards, loans, investments, and insurance.

Major investors in Uala include China's tech giant Tencent and Japan's SoftBank. Uala, which faces regional competition from the likes of Brazil's Nubank, Mexico's Stori and MercadoLibre payment arm Mercado Pago is aiming to tap Latin America's largely unbanked population.

"Latin America is 20% digitized against 50% in Europe and 70% in China. I know that digitization will continue," said Barbieri.

"It seems to me a great shortfall of Latin America's democracies that we have so many people outside the system. In 10 years there will be no people outside the financial system." (Reporting by Nicholas Misculin; Editing by Adam Jourdan and Marguerita Choy)