The US Embassy in Tunisia denied on Monday media reports that American troops had arrested Seifallah Ben Hassine, leader of Tunisia's Ansar al-Sharia group, in Libya.
In a statement, the embassy said US troops had not participated in any operation to arrest Ben Hassine.
Tunisian state news agency TAP reported earlier that American and Libyan forces had arrested Ben Hassine and several of his aides.
Washington blames Ben Hassine for the killing of US Ambassador to Libya Christopher Stevens in the eastern city of Benghazi in September of 2012.
Ben Hassine is wanted by Tunisian authorities on multiple terrorism charges.
He was imprisoned in Tunisia when the 2011 uprising toppled the regime of autocratic president Zine al-Abidine Ben Ali. He was released months later as part of a general amnesty.
In August, the Tunisian government declared his Ansar al-Sharia – one of Tunisia's leading Salafist groups – a terrorist organization, saying it had been implicated in the assassination of two leftist politicians, Chokri Belaid and Mohamed Brahmi, earlier this year.
Belaid was gunned down by militants on February 6 while Brahmi was killed on July 25 under similar circumstances.
The government said it believes the two killings were carried out with the use of the same weapon.
By Reda al-Tamtam
englishnews@aa.com.tr