The NGO said there were an unknown number of casualties on both sides.
In recent days, the IS launched an offensive to take over the industrial area which was previously controlled by the Syrian army.
Meanwhile, Syrian aircraft bombed the Hawijah area on the outskirts of Deir al-Zour, seized by the jihadis last week after fierce fighting that left 33 dead.
The IS proclaimed an Islamic caliphate in late June in territories under its control in Syria and Iraq.
In July, the IS occupied most of the oil-rich Deir al-Zour province, except some neighbourhoods in the capital and the military airport.
The province has been targeted by aircraft of the US-led international coalition which has bombed several oil refineries in the hands of the Sunni extremists.