Southeast Asia's biggest budget carrier, AirAsia, has inked a deal to launch a new low-cost carrier in Vietnam which will take to the skies in August, AirAsia CEO Tony Fernandes said Friday.

The carrier will be known as VietJet AirAsia. AirAsia said the new venture will be its fourth country base, following Malaysia, Thailand and Indonesia.

Fernandes said AirAsia had purchased a 30 percent stake in VietJet Aviation but declined to reveal how much it paid for the acquisition.

"The birth of VietJet AirAsia contributes to the diversification of the aviation market in Vietnam, providing more options by way of low fares to meet the air travel needs of the people," he said.

Fernandes said AirAsia's move into Vietnam was aimed at strengthening its base in Southeast Asia, which has a population of nearly 600 million people, and to open the country as another gateway in the region.

VietJet AirAsia will begin both local and international routes in August, he said.

AirAsia, launched in December 2001 with just two aircraft, is now the region's fourth-largest carrier.