Activists say rebels are attacking a major Syrian army base in the southern province of Daraa.

Ahmad al-Masalmeh, an opposition activist in Daraa, says the attack by rebels of the Western-backed Free Syrian Army began at dawn Tuesday.

He says the rebels aim to capture the base, known as Brigade 52, outside the village of Hirak. He says the rebels have captured the nearby village of Mleiha al-Sharqiyeh.

The Britain-based Syrian Observatory for Human Rights and al-Masalmeh say Brigade 52 is the largest base in Daraa province.

The Observatory says the fighting has killed 20 troops and pro-government gunmen as well as 14 rebels.

President Bashar Assad's forces have suffered several defeats over the past three months at the hands of insurgents as well as the Islamic State extremist group.