Al-Shamy was seen in the city located in Deir al-Zour province along with many of his followers, who evidently were providing security for him, after news reports said he had been killed in an international coalition attack on Friday.
According to the observatory's report Monday, at least nine bodies and 34 wounded people were taken to the hospital in Al-Qa'em, close to Al-Bukamal, after an airstrike by the US-led coalition on the village of Al-Ramana. The attack targeted a building where IS leaders were holding a meeting.
The observatory's sources did not reveal whether IS leader Abu Bakr al-Baghdadi was among those killed or wounded in the attack.
A Pentagon spokesman confirmed that coalition warplanes targeted the meeting near the city of Mosul and destroyed a convoy of 10 trucks being used by the IS personnel.
The IS proclaimed a caliphate in areas under its control in Iraq and Syria last June.