(Adds details, reported killing of French hostage)
By Lamine Chikhi
ALGIERS, March 24 (Reuters) - Algerian Djamel Okacha has been named as a new commander in al Qaeda in the Islamic Maghreb (AQIM), replacing Abdelhamid Abou Zeid who was killed in fighting in northern Mali, Algerian Ennahar TV said on Sunday.
An Algerian security source said Okacha, 34, was very close to AQIM's leader Abdelmalek Droukdel as both belonged to the Group of Algiers, made up of militants born in the region around the Algerian capital.
The source also said that he was confident that al Qaeda commander Mokhtar Belmokhtar, whose death was reported shortly after that of Abou Zeid, was dead.
"Okacha is Droukdel's right-hand man," he said. Okacha's priority would be to reorganize AQIM after it registered the losses of two heavyweight commanders.
France said last week that it had confirmed "with certainty" the death of Abou Zeid, saying that he had been killed in fighting led by French forces in the Adrar des Ifoghas region of northern Mali at the end of February.
It made no comment on Belmokhtar, presumed mastermind of an attack in January at the In Amenas gas plant in Algeria in which more than 60 people were killed, including foreign hostages.
Both commanders' deaths had been reported by Chad, but many analysts remain sceptical about Belmokhtar, noting that his experience and knowledge of the desert terrain could have helped him escape after French-led military operations were launched against the Islamist militants in Mali this year.
Okacha, also known as Yahia Abu El Hamam, joined AQIM northern Mali in 2004, the security source told Reuters.
"He was present at the attack against a military barracks in Mauritania in 2005, and he was also present in the killing of an American in 2009," the source said, referring to aid worker Christopher Leggett.
Algerian security sources had said earlier they believed Abou Zeid and Belmokhtar were together when they were killed.
"I strongly believe that Belmokhtar is dead," the security source said.
A jihadist quoted by the SITE monitoring service on March 3 rejected reports that Belmoktar had been killed, saying he was alive and would soon release a message. No message has been released.
Belmokhtar represented an important link to al Qaeda's roots, having trained in Afghanistan in the early 1990s.
France launched a joint military campaign with some African armies in Mali in January after Islamist rebels took control of the north of the country and began a move south towards the capital Bamako.
On Sunday, Mauritania's news agency ANI reported that AQIM had beheaded a French hostage, Philippe Verdon, captured in northern Mali two years ago. AQIM said other French hostages were at risk because of France's intervention in Mali. (Writing by Myra MacDonald; Editing by Stephen Powell)