"Five of our fighters were martyred and several wounded while repelling two attacks" in Deir Ezzor province, the Syrian Democratic Forces (SDF) said in a statement.

They were among "a series of organised terrorist attacks" in the province, the SDF said, adding: "Our forces... have intensified security measures and increased patrols throughout the region."

The SDF played a key role in the US-backed campaign against IS, which culminated in the jihadists' loss of their last territory in Syria in 2019.

But IS holdouts continue to wage deadly attacks from hideouts in remote areas and are particularly active in the vast Syrian Desert.

The Syrian Observatory for Human Rights has reported a decrease in IS attacks in areas under the control of the central government in Damascus since Islamist-led rebels toppled longtime ruler Bashar al-Assad in December.

The SDF-controlled northeast, however, has seen an increase in attacks, according to the Britain-based war monitor.

The Kurds established de facto autonomy in the northeast in the early years of the civil war which broke out in 2011.

But SDF chief Mazloum Abdi signed an agreement with interim President Ahmed al-Sharaa last month to integrate Kurdish institutions into the Syrian state.