Nigeri is said to be close to the overall commander of the kidnappers, Mokhtar Belmokhtar, a veteran of fighting in Afghanistan in the 1980s and Algeria's civil war of the 1990s who now has links with al Qaeda in the region.

Belmokhtar appears not to have been present during the raid, which led to the deaths of an unspecified number of hostages. More than 20 foreigners were still missing or being held captive in the industrial gas plant on Saturday.

Nigeri was reported to be holed up in the plant near the town of In Amenas and holding seven hostages, according to the Mauritanian reports carried by the SITE monitoring service.

Another of the group's leaders, Abu al-Bara'a al-Jaza'iri, had been killed at the gas field's residential complex, which has been retaken by the Algerian army, according to the ANI news agency.

Mauritanian news agencies have maintained contacts with Islamist groups in the region.

Nigeri joined the hardline Salafist Group for Preaching and Combat (GSPC) in 2005 and participated in several of its "major" missions in Mali, Mauritania and Niger, including a June 2005 attack on a barracks in Mauritania where 17 soldiers were killed, the reports said.