Explosions were heard Sunday inside a U.S. military base in the al-Tanf area in southeastern Syria, state news agency SANA reported.
The Syrian Observatory for Human Rights said the explosions occurred after U.S. helicopters flew in the area.
The UK-based watchdog group said the reasons behind the explosions were not immediately known.
It added the explosions came almost 10 days after the United States fired missiles against militias in eastern Syria from the al-Tanf base.
