The Syrian regime announced the killing and wounding of dozens of civilians in a "terrorist" attack on a bus in the east of the country, without specifying who carried out it.

Meanwhile, residents and opposition sources said that it was an ambush targeting the army and causing more losses.

The Syrian News Agency (SANA) of the regime said that a bus was attacked by a "terrorist" on the Deir Ezzor-Palmyra road in the Kebajib area, killing 25 citizens and wounding 13 others.

However, an opposition military commander told Reuters that the bus was carrying soldiers and gunmen loyal to the regime, returning from vacation on their way to their base in the region.

Another source stated that at least 30 soldiers were killed, most of them from the Fourth Corps, which is the elite of the regime's army, and that it is spreading in the oil-rich region since the expulsion of ISIS fighters from it at the end of 2017.

The Syrian Observatory for Human Rights said that the attack - which it described as one of the "deadliest" attacks since the elimination of ISIS - resulted in the killing of 37 soldiers, including 8 officers, and wounding about 10 others, some of them "critical".

He added that the ambush included bullets and the detonation of bombs, and that two other buses carrying soldiers managed to escape.

Residents in Deir Ezzor and intelligence sources say that recent months have witnessed an increase in the lightning attacks carried out by ISIS remnants, who hide in caves in the desert region.

They also say that the Arab tribes that inhabit the region have been furious in the past few months after the execution of dozens of Bedouins suspected of belonging to ISIS by Iranian militias operating in the area.

The Syrian regime's Ministry of Defense had previously said that ISIS had returned to activity in the Syrian desert through surprise attacks and explosions.

In April, 27 members of the regime forces were killed in an ISIS attack in the vicinity of the desert city of Sokhna (central), which is controlled by the regime's army.