By Adama Diarra and Tiemoko Diallo
BAMAKO, May 27 (Reuters) - Mali's Defence Minister Soumeylou Boubeye Maiga resigned on Tuesday, less than a week after an embarrassing defeat of army forces by Tuareg separatist rebels who seized several northern towns.
The Malian army had launched a surprise assault on the rebel stronghold of Kidal last Wednesday but was overrun by rebel forces, who said they subsequently captured seven other northern towns as U.N. and French peacekeepers declined to intervene.
The failed action threatened to sink struggling peace negotiations between the government and the rebels, and plunge the impoverished West African country back into war.
The government has said that President Ibrahim Boubacar Keita had not given any order for the army's botched attempt to retake Kidal and it launched an inquiry into the matter.
"The president of the republic, on the recommendation of the prime minister, names Bah N'Dao as minister of defence," according to a short decree read on state television by a presidency official.
Sources close to Maiga, a veteran politician appointed when Keita took office in September, said he had presented his resignation earlier on Tuesday.
N'Dao, a retired colonel, was an aide to former President Moussa Traore, who seized power in a 1968 coup, a defence ministry official said.
Tuareg separatists accepted a cease-fire agreement on Friday brokered by the chairman of the African Union and U.N. special representative in Mali. The United Nations is slowly deploying a 12,600-strong peacekeeping mission to Mali as France seeks to wind down its military presence there.
The government has accused the separatists, including the National Movement for the Liberation of Azawad (MNLA), of renewing their former alliances with al Qaeda-linked Islamist groups.
Mali was plunged into chaos in 2012 after Tuareg independence fighters teamed up with armed Islamist groups to seize the north following a coup in the capital.
When they were sidelined by the better-equipped Islamists, the separatists broke with their allies. A French-led military operation routed the Islamists last year.
The MNLA says it controls at least seven northern towns in addition to Kidal and that government troops either abandoned their positions and sought refuge at the camps of the U.N. peacekeeping mission MINUSMA or fled south on Wednesday. (Reporting by Adama Diarra; Writing by Daniel Flynn; Editing by Steve Orlofsky and Ken Wills)