TUNIS (Reuters) - Tunisian President Moncef Marzouki testified on Thursday before a judge probing the murder of opposition leader Chokri Belaid, as police narrowed their hunt for his killer to an area near the border with Algeria.
The shooting of secular politician Belaid by a suspected Islamist radical on February 6 provoked the biggest street protests in Tunisia since the overthrow of strongman Zine al-Abidine Ben Ali two years ago.
Secular parties later withdrew their support for Islamist-backed Prime Minister Hamadi Jebali, forcing the collapse of his coalition government.
Marzouki, who leads one of Tunisia's main secular parties, was called to testify because he had warned Belaid in January of a death threat against him and offered him police protection, local media reported.
Secularists had long complained that Jebali's government was too tolerant of religious radicals emboldened by the fall of Ben Ali, whose government spent decades suppressing Islamists.
A swift arrest and trial of Belaid's killer could calm the political turmoil that has stalled efforts to rebuild an economy hit hard by the 2011 uprising.
"The investigating judge at ??the Court of Tunis heard on Thursday morning President Moncef?? ??Marzouki as a witness in the case of Chokri Belaid's?? ??assassination??," the presidency said in a statement.
The interview took place at the Carthage Palace, the head of state's official residence.
It was the first time a Tunisian president had taken the witness stand in a judicial investigation.
Police believe Belaid's killer is a 34-year-old member of a radical Islamist Salafi group.
Interior Minister Ali Larayedh said on Tuesday that police had arrested four other ultra-orthodox Salafis suspected of being accomplices.
"Chokri received many death threats by telephone in his final weeks," said Belaid's brother Abd Majid.
Zied Lakdhar, a member of Belaid's Popular Front party, also said Belaid had refused police protection.
Army and police forces backed by military aircraft were searching the regions of Wad Mliz and Ghar Dimaou near the border with Algeria on Thursday in an effort to catch Belaid's killer, security sources said.
(Reporting By Tarek Amara; Editing by Tom Pfeiffer)