Renegade Malian soldiers declared on state television on Thursday they had seized power in the West African state in protest at the government's failure to quell a nomad-led rebellion in the north.
Former colonial power France said it was suspending security cooperation with Mali and urged constitutional order to be re-established promptly, a call echoed by the European Union.
The coup has been fronted by soldiers of the rank of captain or lower and, if successful, will add a new layer of insecurity to a Saharan region battling al Qaeda agents and a flood of weapons trafficked from Libya since the fall of Muammar Gaddafi.
The army has for weeks appealed to the government for better weapons to fight the northern Tuareg rebels, now bolstered by heavily armed ethnic allies who fought on Gaddafi's side last year but have returned to Mali.
Members of the newly formed National Committee for the Return of Democracy and the Restoration of the State (CNRDR) read a statement after heavy weapons fire rang out around the presidential palace in the capital Bamako throughout the night.
The CNRDR ... has decided to assume its responsibilities by putting an end to the incompetent regime of Amadou Toumani Toure, said Lieutenant Amadou Konare, spokesman for the CNRDR.
We promise to hand power back to a democratically elected president as soon as the country is reunified and its integrity is no longer threatened, Konare, flanked by about two dozen soldiers, said in a statement marred by sound problems.
A subsequent statement by Captain Amadou Sanogo, described as president of the CNRDR, declared an immediate curfew until further notice. Little is known about Sanogo except that he is an instructor at a military training college.
The CNRDR declared all land and air borders shut, but it was impossible to verify whether the mutiny had sufficient support to seal off a country twice the size of France and with seven neighbours. Earlier a Reuters reporter said Bamako airport had been shut down by local police rather than renegade soldiers.
While no deaths were reported, an official at the Gabriel Toure hospital in central Bamako said around 20 people had been admitted with bullet wounds, with some in a serious condition.
Government and military sources told Reuters the mutineers entered the presidential palace overnight after it was vacated by Toure and his entourage. A defence ministry source said Toure - a 63-year-old former coup leader due to step down after April polls - was in a safe location but his whereabouts were unknown.
GOLDMINER SHARES PLUMMET
His decade-long rule has been among the most stable in the region. But the gold- and cotton-producer has struggled to contain a northern rebellion in which dozens have been killed and nearly 200,000 civilians have fled their homes.
U.N. Secretary-General Ban Ki-moon called for calm and for grievances to be settled democratically. The African Union said it was deeply concerned by the reprehensible acts currently being perpetrated by some elements of the Malian army.
Foreign Minister Alain Juppe said in a statement France was suspending some security cooperation with Mali.
We will maintain our aid to the population, particularly food aid, and we will continue our efforts in the fight against terrorism, Juppe said. Along with the United States, France has sought to bolster efforts by regional governments to combat local al Qaeda agents.
Investor nerves over Mali's gold sector - a key export earner for the country - sent shares in London-listed miner Randgold Resources down 15 percent, despite a company statement that its operations there were not affected.
Sporadic heavy weapons and tracer fire rang out in Bamako through the night and the mutineers, who say they lack the arms and resources to face the separatist insurgency in the Sahara, temporarily forced the state broadcaster off air.
As day broke, a Reuters correspondent saw soldiers shooting in the air on the streets of Bamako where, despite the curfew, there were a number of motorists and motorcyclists.
The people are with the (mutinous) soldiers, said one Bamako resident, Adama Tiarra. We want a government that can sort things out, he added. Others, however, said they were firmly against the attempt to unseat Toure's government.
In a sign of the breadth of the army mutiny, two military sources in the northern town of Gao confirmed the arrests of several senior officers in the town, a regional operations centre for the military.
A military source said a trigger for the mutiny was a visit on Wednesday by the defence minister to a barracks in the town of Kati about 20 km (13 miles) north of Bamako.
The minister went to speak to troops but the talks went badly and people were complaining about the handling of the crisis in the north, the source said.
A defence ministry official who was at the meeting said a soldier accused the minister of not giving them means to fight the rebels. Soldiers then began throwing rocks at the minister before taking weapons from the armoury and shooting in the air.
Tuareg fighters seeking to carve out a desert homeland in Mali's north have made advances in recent weeks, including the seizure this month of the key garrison town of Tessalit by the Algerian border.
(Additional reporting by Adama Diarra in Bamako and Richard Lough in Nairobi; Writing by Mark John; Editing by Jon Boyle)