A US military base in Hasakah, northeastern Syria, was attacked, sources said, reports Mehr News Agency of Iran.
The agency, however, did not specify who fired on this American military base.
The New York Times, citing intelligence sources, wrote that Iran's allies are preparing to attack American military bases in Syria and Iraq.
The attack on the American military base in Syria followed the United States' strikes on three Iranian nuclear facilities: Natanz, Fordow and Isfahan.
US President Donald Trump announced that the aim of the attack was to limit Tehran's nuclear capabilities, and claimed that the main uranium enrichment facilities were completely destroyed.
The Pentagon also announced that it would take time to assess the final impact of the strikes, the newspaper writes.
The United States has called on Iran to make peace, but has threatened new strikes if it responds to the nighttime attack.
The Islamic Republic's Foreign Ministry has said Tehran reserves the right to defend its interests through self-defense.
Amid the tensions, US troops stationed at military bases in the Middle East have been put on high alert.
