U.S. intelligence agencies have reported the movement of Russian artillery units close to the front lines in Syria, the Wall Street Journal reported Wednesday.
The move has prompted concerns in Washington that Moscow and Damascus may be preparing for a new large-scale operation, an unidentified U.S. defense official told the paper.
Russian artillery units have been moving toward the opposition stronghold of Aleppo and closer to Syrian government troops in Latakia, the official was quoted as saying.
The redeployment of artillery was first spotted two weeks ago. Intelligence indicates that the units have since been used to back Syrian government forces in attacks against al Qaeda affiliated group Nusra Front, according to the report.
The cease-fire brokered in Syria by Russia and the United States has largely held since it took effect on Feb. 27. The Nusra Front and Islamic State groups are excluded from the truce.
The Islamic State is a terrorist organization banned in Russia.