Police in the Yemeni capital Sanaa are investigating gunfire near the U.S. embassy, hours after the embassy said it received a warning about an attack.
The shooting was reported Monday at a checkpoint outside the embassy. The U.S. State Department says Yemeni security personnel exchanged gunfire with an unknown group.
Yemeni officials said they were questioning three men in connection with the case.
U.S. officials said there was no damage to the embassy and all U.S. personnel were safe and accounted for.
The embassy had earlier warned Americans to exercise caution in Yemen. U.S. personnel said they had received a threat against the embassy.
Suicide bombers attacked the embassy in September, killing at least 12 people along with six militants. Al-Qaida's branch in Yemen claimed responsibility for the attack.
Yemen is the ancestral homeland of al-Qaida leader Osama bin Laden.