beirut u.s.-backed syrian militias say russian warplanes strike position deir al-zor province monday moscow deny generate friction two rival campaign islamic state syrian democratic force sdf alliance kurdish arab militias fight u.s.-led coalition say attack kill one fighters injure two major-general igor konashenkov russia defense ministry cite ria news agency issue denial say russia always careful ensure air strike accurate spokesman u.s.-led coalition colonel ryan dillon say round hit area around sdf could confirm fire russia war monitor syrian observatory human right say russian round hit sdf near deir al-zor sdf late say respond source fire target near city deir al-zor monday morning without specify force attack russia unite state back separate offensives islamic state eastern syria advance oil-rich deir al-zor province border iraq assault converge islamic state opposite side euphrates bisect province jihadists last major foothold syria river often act divide line proximity time raise risk clash could stoke tensions compete world power russian air support iran-backed militias syrian troop advance along west bank river kurdish commander sdf approach along east bank u.s. jet special force tell reuters monday alliance expect completely push islamic state former syrian headquarter raqqa within month kurdish ypg militia forefront sdf say last week seize 80 percent raqqa battle city enter final stag come days battle intense ... say jihan sheikh ahmed spokeswoman offensive expect plan able liberate raqqa less month right self-defence sdf also capture large gas field euphrates bank saturday russian regime force mount treacherous attack force ... artillery aircraft sdf say statement stand arm cross use legitimate right self-defense monday russia deputy foreign minister sergei ryabkov say u.s. policy syria blame death shell russian general valery asapov near deir al-zor defense ministry moscow announce sunday ryabkov call question u.s. commitment fight islamic state accuse try slow syrian army advance last week pentagon accuse moscow bomb sdf position eastern side river russia deny warn unite state would target sdf force come fire dillon spokesman u.s.-led coalition say communicate russia ensure measure avoid unintended conflict offensives follow u.s.-backed alliance say russian jet strike fighters east syria