US ambassador to Libya Christopher Stevens is confirmed to have died in Tuesday's conflict in Libya's eastern city of Benghazi, the pan-Arab Al Jazeera TV reported Wednesday.

Hundreds of protesters, angered by an alleged US-made movie that insults Prophet Mohammed, broke into the US consulate building in Benghazi on Tuesday night.

The US ambassador, who was on a short trip to Benghazi, died from suffocation as a result of smoke inhalation, as protestors set fire at the scene. Three staffers were also killed during the fierce clashes.

"One American staff member has died and a number have been injured in the clashes," Libya's Supreme Security Committee spokesman Abdel-Monem Al-Hurr was quoted as saying by the news channel on Wednesday.

US Secretary of State Hillary Clinton confirmed that "a staff member" has died in Tuesday's conflict.

On Tuesday, several thousands of Egyptians protested in front of the US embassy in the capital Cairo against the same movie, allegedly sponsored by Americans but not by US government or Hollywood industries.

The Egyptian security forces have intensified their deployment around the building. Seven ambulances have been sent to the scene, but no injuries were reported.