BEIRUT/AMMAN: Syrian rebels said they had captured a major base from the Syrian army in the south of the country on Tuesday, a setback that would increase pressure on President Bashar Assad after his recent losses elsewhere.

Syrian officials could not immediately be reached for comment. State TV had earlier said the army had repelled an attack in the area near the Jordanian border targeted by the rebels early on Tuesday.

“We announce the liberation of Liwa 52,” Issam Al-Rayyes, spokesman for the “Southern Front” alliance of mainstream rebel groups, told Reuters. Liwa 52, or the 52nd Brigade, is one of the biggest Syrian army bases in the area.

The southern region near the border with Jordan and Israel is one of the areas where insurgents have inflicted significant defeats on Assad in the last three months, notably the capture of the Nasib border crossing with Jordan on April 1.

Less than 100 km (60 miles) south of Damascus, the area is one of the last major footholds of mainstream rebels who have been eclipsed elsewhere in Syria by jihadist groups such as Islamic State and the Nusra Front, Al-Qaeda’s Syrian arm.

Nusra and other hard-line Islamist groups also have a presence in the south, including Ahrar Al-Sham, which said it was involved in the attack.

The rebels have failed in previous attempts to capture the base.

The report earlier on Syrian state TV said the army had repelled an attempt by “a terrorist group” to infiltrate a military position. It said a number of the attackers had been killed and wounded, including a rebel commander. The air force was carrying out raids in the area, it added.

“The Southern Front” alliance has been coordinating operations against Assad from a joint command center in Jordan. They have received some support from foreign states that want to see Assad gone, including Gulf Arab governments.

“It is very important because it is the second biggest base the regime has (in the south),” said Saber Safar, a former army colonel whose “First Army” rebel group was one of a number of factions that said they took part. He spoke to Reuters via Skype in the early stages of the attack.

The rebels had fired more than 100 missiles at the base during the attack, the opposition-affiliated Orient News TV station said.

Since late March, an alliance of insurgents including the Nusra Front have seized nearly all of the northwestern province of Idlib at the Turkish border. Islamic State has also seized the city of Palmyra from government control.

The setbacks for Assad have prompted Western policymakers to suggest a window of opportunity for a political deal may be opening in Syria.

But the defeats have also triggered renewed statements of support for Assad from Iran, whose backing has been crucial to his survival.