More than 2,000 rebel fighters were reported to have taken part in Tuesday’s assault.
Rebels in Syria say they have captured a major army base in the south of the country.
The Southern Front, an alliance of rebel groups, announced that the base, known as Brigade 52, was “liberated” in an attack on Tuesday morning.
The base, outside the town of Harak, is one of the largest in Deraa province.
Officials have not commented, but if confirmed its fall would be the latest in a string of defeats suffered by the government in the past three months.
At the start of April, the Southern Front captured the Nasib border crossing with Jordan, days after another rebel alliance seized the capital of the north-western province of Idlib.
The jihadist group Islamic State meanwhile took the strategically important central town of Tadmur and the neighbouring ancient ruins of Palmyra last month.
A spokesman for the Southern Front, Maj Essam al-Rayes, told the AFP news agency that at least 2,000 rebel fighters had overrun Brigade 52 in a “short and quick” assault launched at dawn on Tuesday.
“This base was one of the main lines of defence for the regime forces. It was a nightmare, because they used it to shell all the areas to the east of the province,” he said.
The base also lies near a main road running from the capital, Damascus, to the Jordanian border.
The Syrian Observatory for Human Rights, a UK-based monitoring group, said the battle had killed 20 troops and pro-government militiamen, as well as 14 rebels.
Government forces had now withdrawn to the nearby village of al-Dara, it added.
Ahmed al-Masalmeh, an opposition activist in Deraa, told the Associated Press that the rebels had also captured the nearby village of Mleiha al-Sharqiya on Tuesday.
There were no reports about the status of Brigade 52 on state media.
However, the Sana news agency earlier said air strikes in the area had killed at least 40 members of al-Qaeda’s affiliate in Syria, al-Nusra Front.
Rebel positions in Mleiha al-Sharqiya, Karak and Harak were targeted, and attacks elsewhere in Deraa province were repelled, a military source was quoted as saying.
source: BBC NEWS