France's DGSE foreign intelligence service said Tuesday it has received "proof of life" of one of its officers held hostage by Islamists in Somalia since July 2009.

A DGSE source said the service had received from the kidnappers "a reply to a personal question" to which Denis Allex, a French secret agent kidnapped by an Islamist group on July 14, 2009, was able to respond, proving he was alive.

"No detail was given by his captors on the state of his health nor on his location or the conditions in which he is being held," the source added.

The source declined to give further details "for obvious reasons of discretion" given the "particularly difficult" negotiations under way with the kidnappers.

Allex was seized on July 14, 2009, as was another French agent who was held by different captors and freed the following month.

France said the two were in Somalia to help train local security forces but the Al-Qaeda-inspired Shebab militant group that seized Allex accused them of gathering intelligence for the French government.

The Shebab have demanded the immediate end to any political and military support from France for Somalia's fragile central government and the withdrawal of all foreign advisors and private security firms in Somalia.

Somalia has been riven by internal strife for years, with the strongest groups waging a bloody offensive against forces loyal to the weak transitional government.