The United Nations coordination office for humanitarian affairs said they had died in areas close to the Jordanian border due to "scorpion bites, dehydration and diseases transmitted through contaminated water".
"Cars carrying Russian military police and representatives of the Syrian government's border administration entered the Naseeb crossing without a fight", observatory head Rami Abdel Rahman said.
Syrian government forces have taken over the southern Nassib crossing on the border with Jordan as rebels agreed to give up their weapons in a deal with Russian Federation, marking a major victory for Syrian President Bashar Assad.
AMMAN, Jordan-It was little more than three years ago when rebels stormed the Nassib border crossing on Syria's southern border with Jordan.
The Syrian army reached Nasib crossing on Friday for the first time after losing it to the rebels in 2015.
Clashes between both sides rocked the area between Daraa city and Um al-Mayazin.
"The deal was the best we could achieve to save the lives of our fighters", Hussein Abazeed, a rebel spokesperson, told AFP on Friday.
The ceasefire deal - brokered by Russian Federation, a Syrian government ally, on Friday - saw rebels agree to hand over heavy weapons in exchange for security guarantees and safe passage to other areas.
For the past week, Syria's southern Daraa province has been the target of heavy shelling by the Assad regime amid attempts by the latter to reassert control of the region.
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Also high on the agenda is the issue of the remains of USA soldiers missing from the 1950-53 Korean War. Trump had dubbed Kim "Rocket Man" past year , in reference to repeated North Korean missile tests.
The towns of Busra al-Sham, Marba, Jimreen, Kharba, Jbaib and Ghusum have agreed to be reconciled with the Syrian government forces without fighting.
"A hundred buses were supposed to arrive but [the operation] has been postponed to a later date", the rebel spokesman said.
An Islamic State group affiliate, which holds a small pocket in the southwest of Daraa, is excluded from the deal.
The capture of the Naseeb border crossing is another victory for President Bashar Assad's forces, who have regained control of most of the country's key cities from insurgents in recent years with the help of powerful allies Russian Federation and Iran.
Moscow has been brokering talks with rebels in southern Syria that have already seen more than 30 towns agree to fall back under regime control.
Near the start of the government's offensive, Washington indicated it would respond to violations of that deal, but it has not done so yet and rebels said it told them to expect no American military help. "The war and more fighting won't stop the struggles of the Syrian people".
Friday's agreement came a day after Jordan, which hosts more than 1.4 million Syrian refugees and has closed its northern border, said it had managed to convince the Syrian opposition and the Russians to meet again.
The U.N. refugee agency says around 60,000 Syrians have gathered near the Nassib crossing. The information would include those wanted for deserting the army or escaping conscription and military service.
"Securing the return of our Syrian brothers to their homes and ensuring their security in their country lead our discussions with all the parties", he said in a tweet.