The commander of the Libyan rebels fighting against Colonel Muammar Gaddafi has been shot dead, the rebel leadership says.
The Transitional National Council says Abdel Fattah Younes was killed by assailants after he had been summoned before a judicial committee that was looking into the military operations.
Council leader Mustafa Abdel Jalil said the head of the armed cell that killed him has been arrested.
General Younes was Colonel Gaddafi's interior minister until the start of the rebel uprising in February, when he defected to the rebels and headed their military campaign.
A BBC correspondent says reports suggest he was not entirely trusted by the rebel side, nor was his defection forgotten by Colonel Gaddafi's officials.
Mr Jalil says two aides to General Younes were also killed in the attack and there will be three days of mourning in their honour.
Some unconfirmed reports said General Younes and two aides had been arrested earlier near Libya's eastern front.