Libya has made several arrests over an attack on the US consulate in Benghazi that killed the ambassador and three other US nationals, the deputy interior minister told AFP on Thursday.
"The interior and justice ministries have begun their investigations and evidence gathering and some people have been arrested," Wanis al-Sharif said.
He declined to give any details of the number of people in custody or their backgrounds "so as not to hamper the smooth running of the investigation."
Initial reports said that Ambassador Chris Stevens and the three other Americans were killed by a mob outside the consulate in Libya's second largest city late on Tuesday as they tried to flee an angry protest against a US-produced movie deemed offensive to Islam.
But it is now believed Stevens died from smoke inhalation after becoming trapped in the compound when suspected Islamic militants fired on the building with rocket-propelled grenades and set it ablaze.
US officials are investigating the possibility that the assault was a plot by Al-Qaeda affiliates or sympathisers, using the protest against the film as a cover to carry out a coordinated revenge attack on Tuesday's anniversary of the September 11, 2001 attacks in the United States.
The finger of blame initially fell on hardline Sunni Islamists of the Salafist group Katibat Ansar al-Sharia (Brigade of the Supporters of Sharia).
But in a statement Thursday, the group condemned "the accusations without any verification or investigation" which had emerged against it in the Libyan media.