Pro-government forces meanwhile advanced to a second location along the border with Iraq, where they are expected to link up with state-sanctioned militias on the other side. Most of the desert territory is controlled by the Islamic State group.
The state-affiliated Ikhbariya TV station hailed the government's second contact with Iraq with a triumphant step by its correspondent Rabih Dibi over the berm border.
There was no one to greet him on the other side, but he promised "the brotherly forces of Iraq" would link up with them soon.
Iran's state-affiliated Tasnim News Agency published photos of Gen. Qassem Soleimani, head of the Revolutionary Guard's elite Quds Force, praying with Afghan fighters on the Syrian side of the border.
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On Friday, the Syrian coalition established its first toehold on the Iraqi border in three years, with the help of Russian airstrikes against Islamic State militants.
The troops bypassed US special operations forces embedded with local opposition fighters at the Tanf and Zakf desert outposts dozens of kilometers to the south.
In Daraa, rebels and government forces were fighting for control of the city's Palestinian refugee camp, a built-up residential area.
Local resident and media activist Ahmad al-Masalmeh said it was the third time in eight days that pro-government forces tried to advance with tanks under the cover of airstrikes.
"Today's campaign was the most vicious yet," al-Masalmeh said. Major Issam al-Rais, a spokesman for the rebels' Southern Front division fighting in the city, said the battle was "life or death."
A Syrian general, who spoke to The Associated Press on condition of anonymity because he is not authorized to speak to the media, blamed the fighting in Daraa on the rebels.
The army "will not stop its operations until it wipes out the last terrorist in Syria," the general said. He said the military was "committed to the cease-fire" but would respond to any aggression.
A "de-escalation agreement" brokered by Iran, Russia and Turkey in May has not brought any relief for the city, activists said. The agreement covers four zones in Syria where the rebels are fighting pro-government forces.
The activist-run Nabaa Media outlet released footage of thick black smoke rising over the city following a string of blasts. It alleged the government was using napalm-like weapons. The footage was filmed yesterday. The Syrian general categorically denied the claims.
Daraa is an important link on the highway connecting Damascus to Jordan and was once an important source of customs revenue for the capital. It has been contested since the first anti-government demonstrations in 2011.