The Russian Defense Ministry on Sunday denied it had bombed U.S.-backed militias in Syria, saying its planes only targeted Islamic State militants and that it had warned the United States well in advance of its operational plans.

U.S.-backed militias said they came under attack on Saturday from Russian jets and Syrian government forces in Deir al-Zor province, a flashpoint in an increasingly complex battlefield.

The Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab militias fighting with the U.S.-led coalition, said six of its fighters had been wounded in the strike.

But Major-General Igor Konashenkov, a spokesman for the Russian Defense Ministry, dismissed the allegations in a statement on Sunday.

Konashenkov said Russian planes had only carried out carefully targeted strikes in the area based upon information that had been confirmed from multiple sources.

The strikes had only hit targets in areas under the control of Islamic State, he said.