FACTBOX: Mauritania junta leader no stranger to coups

(Reuters) - Mauritanian soldiers overthrew elected President Sidi Mohamed Ould Cheikh Abdallahi in a coup on Wednesday and announced the formation of a military-led ruling council in the northwest African Islamic state.

Below are some facts about Mohamed Ould Abdelaziz, who led the coup and chairs the military "State Council" formed on Wednesday.

- Born in 1956, Abdelaziz joined the armed forces in 1977 and attended a military academy in Morocco before rising through the ranks of the army.

- He set up the elite presidential guard unit known as the BASEP (Presidential Security Battalion), which was the force that arrested Mauritania's President Sidi Mohamed Ould Cheikh Abdallahi on Wednesday.

- Abdelaziz was instrumental in putting down an attempted coup in June 2003 but went on to be one of the architects of the 2005 coup, which was led by Colonel Ely Ould Mohamed Vall and overthrew President Maaouiya Ould Taya, who had been in power since 1984.

- Unlike Vall, who steered Mauritania to elections in 2006 before officially retiring into business, Abdelaziz remained a key player in the establishment, heading the presidential guard and acting as President Abdallahi's military advisor.

- Abdelaziz was one of the four military officers officially dismissed by the president on Wednesday morning. He responded by arresting the president and prime minister, and took up leadership of the State Council which has taken control of the country. The State Council issued a "Communique No. 1" revoking the dismissals.

(Compiled by David Lewis in Dakar; Editing by Alistair Thomson and Mary Gabriel)