President Sidi Ould Cheikh Abdallahi was arrested as troops rolled through the capital Nouakchott and took over the presidential palace and the prime minister’s office.

A statement read on public radio said that the coup was led by the head of the presidential guard, General Ould Abdel Aziz, who had been sacked earlier that morning.

The coup leaders formed a Military State Council and immediately annulled the army appointments made by the president, according to a statement from the information ministry broadcast on the radio.

The president’s whereabouts are unknown, while Prime Minister Yahya Ould Ahmed Waghf was taken to an army barracks near the presidential palace, security sources said.

A spokesman for the ousted president said that the coup was in response to a presidential decree sacking several high-ranking army leaders including General Abdel Aziz.

The president “issued a decree naming several new officers as the head of the presidential guard, the head of the armed forces and the head of the national guard”.

“These officers, three generals, refused to accept the presidential decree and are rebelling against the constitutional order,” the spokesman Abdoulaye Mahmadou Ba said.

The capital of the nation of 3.1 million people was reported to be calm, with little evidence of turmoil, witnesses said.

The coup came less than six months after Abdallahi came to power in elections hailed as a model of democracy for Africa, following a three-year transition after a bloodless coup in August 2005.

Mauritania has been facing a political crisis and on August 4, 48 MPs walked out on the ruling party less than two weeks after a vote of no confidence in the government had prompted a cabinet reshuffle.

A decree read out on national radio early on August 6 replaced General Ould Cheikh Mohamed Ahmed as chief of the army, as well as sacking Abdel Aziz as head of the presidential guard.

Both generals were members of the transitional council which ushered in the elections which Abdallahi won in 2007.

Political observers in Nouakchott said the two generals were accused of being behind the mass walkout of the ruling party’s MPs on August 4.