(Adds Abdallahi's wife refusing to answer questions)

By Vincent Fertey

NOUAKCHOTT, Sept 25 (Reuters) - Mauritania's military-backed government forced the wife of deposed President Sidi Mohamed Ould Cheikh Abdallahi to appear on Thursday before a Senate committee investigating financial mismanagement, witnesses said.

But the toppled leader's spouse, Khatou Mint El Boukhary, refused to answer questions from the Senate panel, which is looking into alleged irregularities in the funding of a charitable foundation she headed.

Abdallahi, the Saharan Islamic state's first freely elected leader who won a presidential ballot last year, was toppled in a bloodless coup last month by military chiefs led by the head of the presidential guard, General Mohamed Ould Abdel Aziz.

Since the Aug. 6 coup, the ruling military junta led by Aziz has kept Abdallahi in detention, ignoring calls from the United Nations, the European Union and the African Union for him to be released and restored to office.

Witnesses said police vehicles went to the Nouakchott home of Abdallahi's wife, Khatou Mint El Boukhary, on Thursday and took her to the Senate to appear before the inquiry committee.

"She refused to talk before the investigating committee, because the committee is not legitimate," Boukhary's daughter, Amal Mint Cheikh Abdallahi, told reporters.

Reporters were not allowed to attend the hearing, which was held behind closed doors. Abdallahi's wife later returned home.

Abdallahi's son, Ahmed, said the country's military rulers were using "intimidation tactics" and ignoring warnings from the international community that they faced isolation unless they restored the elected president to office.

Aziz, who staged the Aug. 6 coup after Abdallahi ordered his dismissal, has accused the detained president of being incapable of solving the country's economic and security problems and of blocking Senate moves to investigate his wife's foundation.

Gunmen killed 11 Mauritanian soldiers and a civilian guide last week in an attack claimed by al Qaeda's North Africa wing in the West Saharan state, which is a major exporter of iron ore and became a small oil producer in 2006.

The attack raised fears of further strikes by al Qaeda, which has claimed previous attacks against the Mauritanian military and called for a "holy war" following last month's coup. Al Qaeda said "infidel states", the United States, France and Israel, probably had a hand in the military takeover.

Mauritania's coup leaders have appealed to the West for support against what they call a serious terrorism threat.

But this week, the African Union's Peace and Security Council said in a statement the coup leaders should restore Abdallahi to power by Oct. 6 or face the risk of "sanctions and isolation".

The United States and France have already suspended some non-humanitarian aid, which had included U.S. counter-terrorism training for Mauritanian troops. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/) (Additional reporting by Hachem Sidi Salem; Writing by Pascal Fletcher)

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