One American official was killed when armed men stormed the US consulate in the eastern Libyan city of Benghazi during a protest over a film they said offended Islam, Al Arabiya broadcaster reported on Wednesday, DPA reported.
Another US official was injured in the clashes that erupted between the armed protesters and security guards around the consulate in the eastern Libyan city of Benghazi.
The group have set the consulate building on fire, the report added.
The US State Department issued a statement confirming that its office in Benghazi was attacked by a group of militants and that it was working with the Libyans to secure the compound. It didn't confirm the death or the injury, but added, "We condemn in strongest terms this attack on our diplomatic mission."
The attack came after Islamists in neighbouring Egypt scaled the walls of the United States embassy in Cairo on Tuesday in an unprecedented security breach.
Hundreds of protesters remained in front of the embassy into the late hours of Tuesday even after additional soldiers were sent to the area to prevent protesters from storming the embassy.
Several protesters climbed up and onto the walls of the embassy, tore down the US flag and raised a black flag before they were removed by security reinforcements who were rushed to the area.
US State Department spokeswoman Victoria Nuland said Tuesday in Washington the embassy was "working with Egyptian authorities to restore order and get the situation back under control."
She also urged observers not to draw conclusions about US-Egyptian relations based on the incident, pointing to progress made in engaging with civil society. The US hopes protests will remain peaceful and it will continue to support Egypt's democratic transition, Nuland said.