Syrian rebels seized a major air defense base Saturday in a strategic region in the south near the Jordanian border, the latest battlefield triumph for fighters seeking to topple President Bashar al-Assad, activists said.

Fighters with a rebel group active in the south stormed the base, used by the 38th Division, after a 16-day siege, according to a statement posted on Web sites of the group known as the Yarmouk Martyrs Brigade. The base, near the village of Saida in Daraa province, is situated along the international highway linking the Syrian capital, Damascus, with Jordan.

Fighting in Syria’s southern provinces bordering Jordan and Israel has escalated sharply in the past few days. The Syrian Observatory for Human Rights said dozens of people, mostly opposition fighters, were killed in heavy clashes this week in the Quneitra region along the cease-fire line between Syria and Israel in the Golan Heights.

The Britain-based group, which relies on a network of activists on the ground, said that it had documented the deaths of 35 opposition fighters and that contact had been lost with more than 20 others thought to have died in the fighting.

If the rebels were to take over the Quneitra region, it would bring radical Islamist militants to a front line with Israeli troops. The rebel force comprises dozens of groups, including the powerful al-Qaeda-linked Jabhat al-Nusra, also known as the al-Nusra Front, which the Obama administration labels a terrorist organization.

The Observatory said al-Nusra was among the forces that seized the air base in Daraa. Both the rebels and the Observatory reported that the opposition fighters killed the base commander.

In Damascus, supporters of Assad gathered downtown amid tight security for the funeral of a prominent pro-government Syrian cleric slain in a mosque bombing Thursday. The death of Mohammed Said Ramadan al-Bouti, 84, was a blow to Assad, who vowed Friday to avenge the killing, saying he would “purge” the country of the militants behind it.

Assad and the rebels seeking his ouster have blamed each other for the bombing at the mosque.

In Egypt, members of Assad’s minority sect who oppose his regime began a two-day meeting that organizers described as the first of its kind amid concerns about their fate in a post-Assad Syria.

Rebels fighting to end Assad’s rule are mostly from the country’s majority Sunni sect. Assad is Alawite, a Shiite offshoot of Islam. Members of the Alawite community, who make up about 12 percent of Syria’s population, have either rallied behind Assad or stayed quietly on the sidelines of the civil war.

The meeting of about 50 Alawites reflects fear among members of the tiny sect that they would fall victim to revenge killings and assassinations should Assad’s government fall. They plan to seek assurances from opposition chief Mouaz al-Khatib, who might attend the meeting Sunday.

— Associated Press

Albert Aji in Damascus contributed to this report.