The African Union (AU) has suspended Niger after soldiers seized the president and dissolved the country's constitution.
The move, announced after a meeting of the body's peace and security council on Friday, followed condemnation of the coup by France, the former colonial power, and the West African economic bloc, Ecowas.
"As of today, Niger will not be represented in our activities," Mull Sebujja Katende, who presides over the AU peace and security council, said.
"We have condemned the coup and imposed sanctions on Niger. Niger is suspended from all activities of the AU."
An Ecowas delegation was expected in Niamey, the capital, hoping to meet the coup leaders, who are calling themselves the Supreme Council for the Restoration of Democracy (CSRD).
"The team will make its stand known to the junta leaders as well as meet other stakeholders in the Niger political landscape," an Ecowas official in Abuja, the capital of Nigeria, said on condition of anonymity.
The regional body earlier said that it rejected "any change of power through unconstitutional means and violence".
Ban Ki-moon, the United Nations secretary-general, also condemned the coup and called on authorities in Niger to follow up on pledges to restore constitutional order.
But Ban also criticised Mamadou Tandja, the country's president, for seeking to stay in office beyond his second term.
Ban "condemns the coup d'etat that took place in Niger and reiterates his disapproval of unconstitutional changes of government as well as attempts to remain in power through unconstitutional means," a statement from his office said.
The CSRD said shortly after seizing power that it intends to turn Niger into "an example of democracy and of good governance".
However, Salou Djibo, the country's de facto leader, made no mention of plans to hold democratic elections in his first public appearance on Friday.
"For the moment we are at a starting point, and we will create a consultative body," he said.
An Al Jazeera contact in Niger, who cannot be named due to security reasons, said that people in Niamey were getting on with their daily lives, despite a heavy military presence.
"This morning we toured the city and found out that the military that took power have left their tanks and vehicles in some strategic points of the city," he said.
"This is normal following a coup d’état, in order to secure these areas."
After an overnight curfew, markets, schools and banks were all open as usual, witnesses said.
Soldiers stormed the presidential palace on Thursday, seizing Tandja and some of his aides after a four-hour gunbattle.
Sources: Reuters, CIA World Factbook
||Population of 15.3 million according to a 2009 estimate
||Declared independence from France in 1960
||Official language French with several local languages also spoken
||Main religion Islam with Christian minority in south and traditional African religions also practised
||One of world's leading producers of uranium, accounting for about 7.5 per cent of world's supply
||Two-thirds of country is desert, with only fertile area along Niger River
At least three people were reported to have been killed in the gunfight.
Tensions had been high in Niger since President Tandja dissolved parliament last year and changed the constitution to extend his rule following a referendum - a move that drew widespread criticism at home and led to international sanctions.
Marie-Roger Biloa, founding editor of the Africa International magazine, said some sort of action had been expected.
"Nigeriens are very proud of their democratic process," she told Al Jazeera from Paris, where she is based.
"They [Nigeriens] have been really trying to put a democratic institution in place, and everybody was expecting something to happen after President Tandja decided not to play by the rules."
Last June, Tandja dissolved the constitutional court that had ruled against him and assumed the power to rule by decree, brushing aside international criticism of the move, saying he was answerable only to the people of Niger.
He was supposed to step down in December following two five-year terms in a row, but his so-called reforms removed most checks on his authority, abolished term limits and gave him an initial three more years in power without an election, an extension he said he needed to complete large-scale investment projects.