The army said the attacker, a Syrian national, was detained and taken to hospital for treatment and soldiers were searching through the area for other gunmen.
The US embassy said a small arms fire was reported near its entrance in the morning. The facility and staff were safe, it added. US ambassador Lisa Johnson is currently travelling outside Lebanon, according to diplomatic sources.
A Lebanese security source told Reuters that Lebanese troops wounded the gunman in the stomach.
The security source also said a member of the embassy’s security team was lightly wounded. An embassy spokesman did not respond to a Reuters question on any injuries among the embassy guards.
Reuters verified pictures of the suspected attacker circulating online and geolocated them near the embassy. Reuters verified part of the Arabic writing on his vest, which read “Islamic.” There was no immediate claim of responsibility for the attack.
A Reuters cameraman saw Lebanese security forces setting up checkpoints around the embassy as a US-made helicopter provided to the Lebanese army circled above.
Lebanon’s caretaker prime minister Najib Mikati said he was following up on the incident with the defence minister and security forces.
The US embassy lies north of Beirut in a highly secured zone with multiple checkpoints along the route to the entrance. It moved there from Beirut following a suicide attack in 1983 which killed more than 60 people.
In September, shots were fired near the embassy with no injuries reported.
In mid-October, in the early days of the Gaza war, scores of protesters gathered outside the embassy to demonstrate. Lebanese security forces used tear gas and water cannon to repel them.
Lebanon has been the scene of conflict between Iran-backed Hezbollah and Israel since October in parallel to the Gaza war. Tens of thousands of people on both sides of the Israel-Lebanon border have been uprooted amid fears that the war will deepen.
The US has been making diplomatic efforts to ease violence along the border.
In a separate incident, a member of Lebanon’s internal security forces assigned to provide security at the Saudi embassy in Lebanon committed suicide outside the embassy on Wednesday, a security source and a diplomatic source said.
The security source said the embassy guard died after shooting himself in the head. The diplomatic source said he suffered from mental health conditions.