Libyan authorities have arrested at least 50 people in the wake of last week’s killing of US ambassador Chris Stevens in an attack in the city of Benghazi.

Libyan authorities have arrested at least 50 people in the wake of last week's killing of US ambassador Chris Stevens in an attack in the city of Benghazi following the broadcast of the US offensive film against Islam, Libya's parliament chief said Sunday.

"The number reached about 50," Mohammad al-Megaryef, president of the Libyan National Congress, told CBS News in an interview.

Stevens and three other Americans were killed on Tuesday when suspected militants fired on the US consulate in the eastern Libyan city with rocket-propelled grenades and set it ablaze.

Megaryef said "a few" of those who joined in the attack were foreigners, who had entered Libya "from different directions, some of them definitely from Mali and Algeria."

"The others are affiliates and maybe sympathizers," he added.