Mozilla claims its new mobile operating system Firefox is now available in 13 countries following news that Telenor has launched Firefox-based devices in Serbia.

The operator announced that the Eastern European market is now up and running with Firefox software via Alcatel’s One Touch Fire device. Hungary and Montenegro will be switched on before Christmas. “Asian markets will follow,” added Telenor.

The move follows the announcement at Mobile World Congress in February that more than 20 operators and handset vendors would support the new platform. The HTML5-based OS is designed to bring a smartphone experience at a low price point, with a particular focus on emerging markets.

Telefonica has arguably been the staunchest supporter of the Firefox OS, launching the world’s first device in Spain in July. Other Telefonica markets such as Colombia and Venezuela followed.

Deutsche Telekom is another tier one operator to have already pushed the platform live. Its subsidiaries in Poland, Germany, Hungary and Greece are already supporting the Firefox OS.