"It’s a big crowd – I can’t even estimate how many people – but I can tell you, thousands of people," says RFI's Hausa service correspondent Lydia Addo.
The junta, which has called itself the Coordination of Democratic Forces for the Republic (CSRD), called for its supporters to “participate massively” in the rally.
"I’m not very surprised because people have been so frustrated, by the stubbornness and dictatorial tendencies of Tandja, that any change would be welcome," says Jibrin Ibrahim from the Centre for Democracy and Development.
US Deputy Assistant Secretary of State William Fitzgerald said on Friday that his country’s position was clear as long as the coup against Tandja would ensure the restoration of democracy.
“They have got to show as soon as possible that are genuinely seeking to restore the constitution and to move to a return to democratic and civilian rule,” he said.
UN Secretary-General Ban Ki-moon condemned the coup, appealing for “calm and for the respect of the rule of law, and of the human rights of all Nigeriens”.
While the African Union announced the suspension of Niger from its organisation on Friday. Mull Sebujja Katende, who is responsible for the peace and security council, said they condemned the coup and have “imposed sanctions on Niger”.
They want Niger to revert to the constitution which was in place before the referendum that enabled Tandja to remain in office.
Ibrahim, who has been following the political crisis in Niger, told RFI that public opinion will depend on how quickly the country is returned to democratic rule.
"They [the junta] can only be welcomed on the basis that they will now create a situation for a very quick and speedy return to democratic and constitutional rule," says the Zaria-based analyst.
Addo, who's in Niamey, agrees with Ibrahim. She says "people are waiting for the formation of the military government".
"During the meeting today, the political opposition asked the military to come back to democracy urgently," she added.