A car bomb blast killed at least four civilians at a camp for displaced Syrians by the border with Jordan, the Syrian Observatory for Human Rights monitor said.
"A car bomb exploded on the outskirts of the Rukban camp on the Jordanian border, killing four displaced people and injuring others," said Rami Abdel Rahman, director of the Britain-based monitor.
Jordan's official Petra news agency, citing a military source, also reported the blast at the isolated makeshift camp, which houses around 85,000 Syrians according to the United Nations.
The source said 14 wounded people had been taken to a clinic in the border area for treatment, adding that no decision had been taken yet on whether they would be transported to Jordanian hospitals.
The source added that there were no Jordanian casualties in the blast.
Jordan closed its nearby border in June 2016, halting aid deliveries to the camp, after a bombing claimed by the Islamic State jihadist group killed seven Jordanian soldiers.
Jordanian officials said at the time that the bomber had come from the camp and declared the borders a closed military zone.
The decision prompted shortages at the camp, with rights group Amnesty International in October decrying "hellish" conditions for those seeking refuge there.
Aid has been delivered to the camp only twice since the border was closed, most recently in November, when the UN supplied food, hygiene kits and winter clothing.
The United Nations says there are more than 600,000 refugees from Syria in Jordan, a figure Amman puts at 1.4 million.
In August, King Abdullah II said his country was "doing its utmost to help refugees" from Syria.
"However, we have reached our limits... This is an international crisis and an international responsibility, and the world has to do its part," he said.
More than four million Syrians have fled their country since the beginning of the conflict in March 2011.
Over 310,000 people have been killed in the violence.