The State Department revealed on Wednesday that the shooter accused of opening fire on the US Embassy in Lebanon earlier in the day was wearing what "appeared to be an ISIS insignia", Fox News reported.

State Department spokesman Matthew Miller said that "one member of the embassy’s local guard force was seriously injured" and the gunman has been arrested following the attack in Beirut that unfolded around 8:30 a.m. local time.

"We are aware that the individual who was arrested was wearing what appeared to be an ISIS insignia, but we are conducting a full investigation with the Lebanese authorities into the actual motivations," Miller added, speaking during a press briefing.

The embassy said in its own statement that "small arms fire was reported in the vicinity of the entrance to the US Embassy", adding, "Thanks to the quick reaction of host country security forces and our Embassy security team, our facility and our team are safe."

The embassy recommended that US citizens in Lebanon monitor its website "for alerts and the news closely for breaking developments that could affect internal security."

Meanwhile, AFP reported that the shooter, who was arrested after the incident, was a Syrian man who carried out the attack "in support of Gaza", said a local judicial official.

A security official told AFP that a Lebanese national working for the embassy suffered light injuries to his eye after the assailant opened fire.

The gunman, who lived in east Lebanon's Bekaa Valley, carried out the attack "alone", added the official.

The Lebanese army later said in a statement that it had arrested five suspects in the case in the Bekaa region, including three relatives of the alleged shooter.