Google's balloon-powered high-speed Internet service known as "Project Loon" began its first tests in Sri Lanka on Monday ahead of a planned joint venture with Colombo, the country's top IT official said.

One of three balloons that will be used in the trials entered Sri Lankan airspace on Monday, the Information and Communication Technology Agency chief Muhunthan Canagey said.

"The first balloon entered our airspace this morning. It was launched from South America." Canagey told AFP. "It is currently over southern Sri Lanka."

He said a Google team was expected later this week to test flight controls, spectrum efficiency and other technical matters.

The government announced earlier this month it would take a 25% stake in a joint venture with Google to deliver a high-speed Internet service powered by helium-filled balloons.

Sri Lanka is not investing any capital, but will take the stake in return for allocating spectrum for the project. A further 10% of the joint venture would be offered to existing telephone service providers on the island.

It promises to extend coverage and cheaper rates for data services.

Service providers will be able to access higher speeds and improve the quality of their existing service once the balloon project is up and running.

The balloons, once in the stratosphere, will be twice as high as commercial airliners and barely visible to the naked eye. The balloons will have a lifespan of about 180 days, but can be recycled, according to Sri Lankan officials involved in the venture.

Official figures show there are 3.3mn mobile Internet connections and 630,000 fixed line Internet subscribers among Sri Lanka's more than 20mn population.

Sri Lanka became the first country in South Asia to introduce mobile phones in 1989 and the first to roll out a 3G network in 2004. It was also the first in the region to unveil a 4G network two years ago.