With Mauritanian President Maaouya Ould Taya out of the country, the armed forces on Wednesday said they had seized power to end his "totalitarian regime" and had set up a military council to rule in his place.
Ould Taya, who himself came to power in a coup in 1984 and has withstood several previous ousting attempts, was overseas as troops seized state media, the armed forces headquarters, and positioned themselves outside the presidency building in the capital, Nouakchott, in the early hours of the morning. The airport was also closed.
Later, in a communique broadcast on state media, a "Military Council for Justice and Democracy" announced it would rule the desert nation, which is hoping to get rich from oil, for a maximum of two years.
"The armed forces and the security forces have unanimously decided to put an end to the totalitarian practices of the defunct regime under which our people have suffered so much these last years," the statement from the hitherto-unknown group said.
"This council vows before the Mauritanian people to create the conditions favourable for an open and transparent democracy."
An IRIN correspondent in the capital reported that hundreds of people had taken to the streets after the declaration. Convoys of cars were tearing around the city's sandy avenues, with youths honking their horns and shouting slogans like "Down with Taya", and "Long Live the Putschists".
Journalists contacted in several other towns around Mauritania reported similar scenes of joy unfolding.
No individual signed off on the council's statement, but military sources and people who were at the state broadcaster when it was taken over, said that the head of the presidential guard, Col Mohamed Ould Abdel Aziz, and the head of national security, Col Ely Ould Mohamed Vall, were involved.
The African Union condemned what it called a "coup attempt".
"The chairperson ... reaffirms the total rejection by the AU of any unconstitutional change of government," a statement by the 53-member organisation said. "He firmly condemns any seizure or any attempt to seize power by force."
There was no immediate reaction from opposition groups in Mauritania, but Ould Taya's ruling Social Democratic Republican Party (PRDS) urged all political entities to denounce the coup.
Ould Taya had been out of the Sahelian country, which straddles black and Arab Africa, attending the funeral of Saudi Arabia's King Fahd, when troops moved in at around 5:00 am.
Hours later, he arrived in Niger's capital, Niamey, but he made no declaration and reporters at the airport were kept away.
The president has reportedly angered many of Mauritania's 2.8 million-strong and staunchly-Muslim population by establishing diplomatic ties with Israel and launching a crackdown on Islamic fundamentalists groups in the country.
Ould Taya was nearly toppled during a bloody uprising in June 2003, which was put down after two days of heavy fighting in the capital by loyal forces. Mauritanian authorities also said they nipped two coup plots in the bud in August and September 2004.
Four army officers were convicted of masterminding the raft of coup plots and were sentenced to life in prison in February this year, while three leading opposition politicians were cleared of bankrolling the operations.
During the trial, some of the officers explained how they had wanted to put a stop to corruption, tribalism, poor pay and mismanagement in the army.
A diplomat in Nouakchott said on Wednesday that the situation was calm, contrasting it with the coup attempt in 2003.
"Last time there was lots of shooting and everyone was very scared. Today, although certain areas of Nouakchott are closed off, round by the radio and TV stations and the presidential palace, the rest of the city is going about its business as normal," he said by telephone
Witnesses said that the homes of some government members were being guarded by soldiers, and there were reports of some army chiefs being arrested, but they could not be independently confirmed.