The Syrian government and its Russian ally pounded rebel-held areas of the southern province of Daraa on Thursday with the heaviest airstrikes of a two-week-old offensive, an AFP correspondent and a monitor reported.
Hundreds of missiles and barrel bombs were unleashed before dawn by both Syrian and Russian aircraft, after talks on rebel surrenders broke down on Wednesday, the Syrian Observatory for Human Rights said.
The intensity of the bombardment allowed government forces to seize control of a security checkpoint on the Jordanian border for the first time in more than three years, the Britain-based monitoring group said.
Observatory director Rami Abdel Rahman said the bombardment was an “attempt to make the rebels back down after they refused to subject themselves to the Russian terms for a ceasefire.”
Some rebel groups have agreed to negotiated surrenders but on Wednesday evening the remainder walked out of talks with a Russian delegation saying they would not agree to hand over their heavy weapons.
An AFP correspondent on the edge of the rebel-held south of the city of Daraa, the divided provincial capital, said the bombing of rebel neighborhoods was the most intense since the launch of the Russian-backed offensive on July 19.
Damascus has unleashed similar bombardment of rebel-held towns elsewhere in Syria in the past that have delivered negotiated surrenders which allowed it to retake swaths of territory.
The violence has displaced between 270,000 and 330,000 people, according to the United Nations, many south to the border with Jordan or west to near the Israeli Golan Heights.
Both countries have kept their borders closed, despite mounting calls by rights groups to let Syrians escape to safety.
IDF chief Gadi Eisenkot and other top military officers traveled to the border on Wednesday to hear updated assessments from soldiers in the field.
Tens of thousands of displaced Syrians have made their way toward the Israeli Golan Heights, settling in overflowing, under-resourced tent cities near the border. In some cases, the displaced person camps are located some 100 meters from the security fence, clearly visible from Israel.
On Wednesday, Human Rights Watch demanded both Jordan and Israel allow asylum seekers in.
More than 140 civilians have died since the assault began.
World powers have criticized the operation for violating a ceasefire that was announced last year by Washington, Amman and Moscow, but that has not halted the blitz.
Times of Israel staff contributed to this report.