French billionaire Xavier Niel’s Atlas Investissement has increased its bid to buy out Latin-American-focused carrier Millicom to $4.4 billion.

The company's initial bid of $4.1bn was rejected after Millicom's board of directors deemed the bid too low.

Niel, the founder of Iliad Group, submitted the bid through his investment vehicle, Atlas Investissement.

Atlas, which already owns a 29 percent stake in Millicom, noted in an open letter to shareholders that it has increased its bid from $24 per share to $25.75.

Millicom has not yet responded to the offer, but previously noted that the initial bid "undervalues the company."

Millicom operates as Tigo across several Latin American markets, serving close to around 50 million mobile customers.

Atlas is the biggest stakeholder in the telco, first scooping a seven percent stake back in 2022.