The Britain-based Syrian Observatory for Human Rights says rebels fighting to topple President Bashar Assad's government launched an assault on the base northeast of the city of Raqqa yesterday.
Rami Abdurrahman, the Observatory chief, says sporadic clashes are still underway today for the complex, known as Base 17, and that at least 24 fighters have been killed in battle.
In February, Raqqa was the first city to fall entirely under rebel control since Syria's crisis erupted in March 2011.