Abdel Fattah Younes, Libyan rebel chief, reportedly killed (VIDEO)

The military commander of the Libyan rebels, Abdel Fattah Younes, was shot dead by assailants, the rebels' National Transitional Council announced late Thursday.

Rebel leader Mustafa Abdel Jalil told the Associated Press that Younes and two bodyguards were killed after being summoned back from the battlefield. Younes was killed before making a requested appearance before a rebel judicial committee, it states.

The National Transitional Council also announced that the head of the group responsible for the deaths has been arrested, BBC reports. There will be three days of mourning for the deaths.

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Younes is a former Libyan interior minister and was involved in a coup that helped bring defiant leader Muammar Gaddafi to power in 1969. Younes defected to rebels in February.

The details surrounded Younes's death remain murky, reports the Christian Science Monitor.

"The rest of the story – who killed him, when, precisely where, and why – all remains murk and conjecture, created by cross-cutting rivalries within the rebellion and the often misleading and contradictory way that Libya's Transitional National Council (TNC) communicates with the press and the Libyan public," it states.

Younes' death represents some of the "schisms" appearing within the rebels' group as they struggle to break a five-month stalemate in the country.

"A lot of the members of the TNC were Gaddafi loyalists for a very long time. They were in his inner circle and joined the TNC at a later stage," Geoff Porter from North Africa Risk Consulting, told the AP. "(The killing) is indicative of schisms that have been appearing within the TNC over the last few months … We might be seeing the most egregious examples of the divisions between the former regime members and the original rebels."

The killings come as the rebels launched an offensive in the west and claimed Thursday to have controlled several towns in the Western Mountains.

The rebels still control most of the east of the country, including Benghazi and the western port city of Misurata. And Gaddafi's forces control much of the west, including the capital, Tripoli.