Rebels on a lightning advance through Syria said on Saturday they have begun to encircle Damascus as government forces denied they had withdrawn from areas near the capital.

Syrian rebel commander Hassan Abdel Ghani sought to reassure religious minorities on Saturday after Islamist-led fighters snatched key cities and swathes of territory from government control.

Syrian opposition activists said insurgents have captured a main border crossing with Jordan forcing Syrian authorities to leave it.

Shortly afterward, Jordan’s Interior Minister al-Frayeh said the Naseeb border crossing with Syria had been closed because of the security situation on the Syrian side.

Gaza's civil defense agency said 29 people were killed on Friday in Israeli strikes near the Kamal Adwan hospital in the northern Gaza city of Beit Lahia, where Israel is pressing a major offensive.

"At least 29 people were killed and dozens were wounded in the northern Gaza Strip since dawn on Friday as a result of the continuing Israeli shelling around Kamal Adwan hospital," said civil defense spokesman Mahmud Bassal.

A war monitor said Syrian government troops pulled out of the central city of Homs on Friday in the face of an Islamist-led rebel offensive, but the defense ministry denied the report.

"Syrian soldiers have withdrawn from Homs city towards its outskirts," said Rami Abdel Rahman of the Britain-based Syrian Observatory for Human Rights monitor. The ministry later said "there is no truth to news... about the army withdrawing from Homs".

The Israeli military said Friday it was "reinforcing aerial and ground forces" in the occupied Golan Heights in response to sweeping Islamist-led rebel advances in Syria.

In a statement, the military said it was "monitoring developments and is prepared for all scenarios, offensive and defensive alike", adding that it "will not tolerate any threat near the Israeli border".

The commander of a Kurdish-led force in Syria said Friday he was open to talks with Turkey and Islamist-led rebels, whose offensive had created a "new political and military reality".

"We want to de-escalate with Hayat Tahrir al-Sham (HTS) and other parties and to solve our problems through dialogue" including with Turkey, Mazloum Abdi, who heads the Syrian Democratic Forces (SDF) that controls swathes of northeast Syria, told reporters. "We were surprised to see the sudden and rapid collapse of Syrian government forces on the frontlines as factions took control of large areas, imposing a new political and military reality," he added.

Syrian troops and their Iran-backed allies "suddenly" pulled out of eastern Deir Ezzor city and its surroundings Friday, a war monitor said, as a rebel offensive dealt the government a series of stunning blows.

"Syrian regime forces and commanders of Iran-backed allied groups suddenly withdrew from Deir Ezzor city and its countryside with columns of soldiers heading towards central Syria," Rami Abdel Rahman, who heads the Syrian Observatory for Human Rights war monitor, told AFP.

A Hamas official says international mediators have resumed negotiating with the militant group and Israel over a ceasefire in Gaza, and that he was hopeful a deal to end the 14-month war was within reach.

Ceasefire negotiations were halted last month when Qatar suspended talks with mediators from Egypt and the United States because of frustration over a lack of progress between Israel and Hamas. But there has been a “reactivation” of efforts in recent days to end the fighting, release hostages from Gaza and free Palestinian prisoners in Israel, according to Bassem Naim, an official in Hamas’ political bureau who spoke with The Associated Press in Turkey on Thursday.

It was one of the darkest moments in the modern history of the Arab world. More than four decades ago, Hafez Assad, then president of Syria, launched what came to be known as the Hama Massacre.

Between 10,000 to 40,000 people were killed or disappeared in the government attack on the central Syrian city. It began on Feb. 2, 1982, and lasted for nearly a month, leaving the city in ruins.