In recent months, Syria's new Islamist government has expanded its control to parts of the country's north and northeast that were previously held by Kurdish-led forces, including areas near the site of Monday's attack.

The government has also formally joined the international coalition against the Islamic State group (IS), which has long launched attacks in those areas.

The two soldiers were killed "and others wounded in a treacherous attack by unknown assailants" on a bus in Hasakeh province, state news agency SANA quoted the defence ministry as saying.

A military source told AFP on condition of anonymity that a military bus "came under gunfire" along the highway between Ras al-Ain in Hasakeh province and Ain Issa in Raqa province, adding that two soldiers were killed and two others wounded.

Investigations were underway to determine who was behind the attack, the source added.

Once in control of large swathes of Syria and Iraq, IS was territorially defeated in Syria in 2019 in a battle spearheaded by Kurdish-led forces with support from a US-led international coalition.

The jihadists however maintain a presence in Syria, mainly in the country's vast desert, and repeatedly attacked Kurdish-led forces while they controlled swathes of the northeast.

In February, after government forces seized control of many of those areas, IS urged its jihadists to fight Syria's new authorities.

Days later, state media said four Syrian security personnel were killed in an IS attack in the northern city of Raqa, which had been recently taken by Damascus's forces.