Mauritania's new junta promised on Thursday to quickly hold new elections as it confronted international condemnation of the detention of the west African country's first democratically elected leader.

Around a thousand people marched through the capital Nouakchott in a show of support for coup leader General Mohamed Ould Abdel Aziz.

The pro-coup demonstrators marched alongside vehicles bearing giant portraits of the general and chanted "Aziz, Aziz" as they wound their way from the international airport to the presidential palace.

"The soldiers guard over us, we have to support them. They correct things every time when we have problems," said a young man holding a portrait of Aziz who did not want to be named.

The march was organised by a group of MPs who walked out of the ruling party last week amidst a political crisis that President Sidi Ould Cheikh Abdallahi accused Aziz and other army chiefs of stirring up.

The coup "is the inescapable result of the way the ousted president conducted state affairs," said Sidi Mohamed Ould Maham, one of the MPs, who addressed the marchers.

He said Abdallahi "blocked the functioning of democratic institutions" and showed "a disregard for the majority opinion".

Abdallahi, ousted after he tried to sack Aziz and other senior army officers, was in custody early on Thursday at the headquarters of the presidential guard, according to a security source.

Police in riot gear were posed at strategic junctions around the capital, but the city was calm as most people went on with business as usual.

The junta said in a statement released in the early hours of Thursday it would "supervise the holding of presidential elections enabling the relaunch of the democratic process in the country and to reshape it on a perennial basis."

It promised: "These elections, which will be held in the shortest possible period, will be free and transparent and will bring for the future a continued and harmonious functioning of all the constitutional powers."

The former interior minister and two other officials considered close to Abdallahi were also arrested, security sources said.

According to the Mauritanian news agency Agence Nouakchott d'Information (ANI), Abdel Aziz met other government ministers on Wednesday afternoon and asked them to stay on in their posts.

The coup triggered international condemnation, with the United States urging the release of Mauritania's leaders and the EU threatening to cut off aid.

UN Secretary General Ban Ki-moon called for "the restoration of constitutional order."

The African Union called for maintaining "constitutional legality" and said its peace and security commissioner, Ramtane Lamamra, would go to Mauritania to "assist in promoting a peaceful solution to the crisis."

The largely desert country has a history of coups since gaining independence from France in 1960, and on the morning after the coup, Mauritanian newspapers echoed a sense of deja-vu.

"Coup d'etat: how did we get back to the starting point?", asked the Le Quotidien de Nouakchott daily. The Biladi newspaper spoke of "Democracy tested" while Nouakchott Info headlined: "Coup d'etat, the end of an era".

The elections that Abdallahi won were 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 Monday 48 members of parliament walked out on the ruling party less than two weeks after a vote of no confidence in the government prompted a cabinet reshuffle.

AFP