DAMASCUS - Rocket fire targeted a US military base in Syria's eastern province of Deir al-Zour on Monday evening, state news agency SANA reported.

The targeted base is located in the al-Omar oil field in the eastern countryside of Deir al-Zour, SANA said, without providing further details.

Meanwhile, the pro-rebel Syrian Observatory for Human Rights said the attack caused damage and burned cars in the base, without any mention of casualties.

The Britain-based watchdog noted that pro-Iran fighters were behind the rocket fire.

Following the attack, areas under the control of the pro-Iranian fighters in the al-Mayadin city in Deir al-Zour witnessed several explosions, which appeared to be retaliatory shelling from the targeted US base in the al-Omar field, said the Observatory.

The exchange of fire comes after the United States carried out a missile strike at 1 am on Monday on pro-Iranian fighters' positions in the eastern countryside of Deir al-Zour near the Iraqi border, killing five.

Washington claims that pro-Iran militiamen are responsible for attacks against US positions in Iraq.