The Syrian army is seeking to advance toward Mayadeen, a city in the province 44 km southeast of Deir Zor, where the river flows through it.
According to Konashenkov, the Russian air group and naval forces continue to support a Syrian government offensive aimed to defeat the terrorist group Daesh in the Euphrates River valley. The group announced its formation on January 23, 2012 as the union of Syrian jihadists, whose ultimate goal is to oust President Bashar Al Assad's regime and establish an Islamic emirate under sharia, or Islamic, law.
Backed by Russian air power, Syrian ground forces have managed to make numerous gains against terrorists on various fronts.
Deaths happened in Deir Ezzor in past 48 hours, but Russian Federation says strikes were targeted at Daesh strongholds in Al Mayadeen.
"They were crossing the river on makeshift rafts in a village south of Mayadeen", SOHR director Rami Abdel Rahman said, adding that three children were among those killed overnight.
It is the latest of a series of accusations traded as Russian-backed troops loyal to Syrian President Bashar al-Assad and the USA -allied, Kurdish-led Syrian Democratic Forces battle IS fighters in the eastern province of Deir al-Zor near the Iraqi border.
IS has seen its self-declared "caliphate" straddling Syria and Iraq shrink steadily over the past two years and has lost all but a few of its main hubs in both Arab states.
Earlier on Thursday, Russia's Rossiya 24 state television channel cited the Russian defense ministry as saying a Russian air strike killed 49 Nusra Front militants including seven of its field commanders in Syria's Idlib province.
The Observatory relies on a network of sources inside Syria, and says it determines whose planes carry out raids according to type, location, flight patterns and munitions used.
Russian Federation has not acknowledged any civilian deaths from its strikes since it intervened in Syria in 2015, and dismisses the Observatory's reporting as biased.
Up to 10 hospitals have been reportedly damaged in the past 10 days, cutting off hundreds of thousands of people from access to health care, the aid agency said in a statement voicing alarm at the situation from Raqqa to Idlib and eastern Ghouta.