A car bomb on Saturday killed at least four people and critically injured a number of others at the Rakban refugee camp in Syria near the border with Jordan, according to the Syrian Observatory for Human Rights, a Britain-based monitoring organization.
The camp is home to refugees and also to rebel groups, including the Jaish al-Ashair, which fight both President Bashar al-Assad and the jihadist Islamic State movement, and was targeted by bombings last year.
More than 75,000 people live in Rakban. Millions of Syrians have fled their homes during the civil war that has killed hundreds of thousands since it began in 2011.
Attacks last year targeted a Jaish al-Ashair checkpoint in the camp in October, killing three people and a military post nearby in July, killing six Jordanian border guards.
Rakban is located in a desert area of the long border between Syria and Jordan, near to territory held by Islamic State, which regards the Syrian and Jordanian governments and other rebel groups as its enemies.
Although Islamic State has lost much of its territory in Iraq and northern Syria since 2015, it has in recent weeks attempted to expand and consolidate its presence in central and eastern Syria with campaigns in Palmyra and Deir al-Zor.