DUBAI (Reuters) - Algerian al Qaeda commander Mokhtar Belmokhtar, reported killed by Chadian troops, is alive, a monitoring service that tracks online militant forums reported a contributor as saying on Sunday.

An unidentified participant in militant website discussions said in a message posted on several forums that Belmoktar was "alive and well and leading the battles himself", the U.S.-based SITE service reported.

The message said Belmokhtar, the presumed mastermind behind a hostage-taking at an Algerian gas plant in January, would soon issue a message confirming the news, SITE reported.

The death of Belmokhtar, nicknamed 'the uncatchable', has been reported several times in the past. On Saturday, Chad said its forces had killed him in the same part of Mali that they had killed Adelhamid Abou Zeid, al Qaeda's other senior field commander in the Sahara, a few days previously.

The killing of Belmokhtar and Abou Zeid, if confirmed, would eliminate al Qaeda's leadership in Mali and raise questions over the fate of seven French hostages thought to be held by the group in the country.

Al Qaeda in the Islamic Maghreb (AQIM) has pledged to avenge a French assault on its fighters in Mali, which Paris said it launched to prevent its former colony becoming a launchpad for wider al Qaeda attacks.

The online participant did not indicate how he learned of Belmoktar's status, SITE reported.

Ahrar Press, an independent Arabic media organization, also reported that a source in Belmoktar's group denied claims of his death, SITE reported.

(Reporting by William Maclean; Editing by Robin Pomeroy)