State television and radio were offline, though the government issued a statement urging calm and saying security forces were mobilising in response.
The attack marked the latest threat to the rule of Abdourahamane Tiani, who seized power in a 2023 coup. Tiani had pledged to improve security in the Sahel nation, a major uranium producer, but jihadist attacks have persisted.
The early morning assault lasted for hours, involving soldiers from the localities of Ouallam, Tera and Dosso in the southwest, according to a Niger security source and Yvan Guichaoua, senior researcher at the Bonn International Centre for Conflict Studies.
Troops in this area have sustained heavy casualties in battles with the regional Islamic State affiliate.
Earlier, a separate Niger security source told Reuters that "terrorists" had attacked the airport and attempted to breach the security perimeter around the presidency. One Reuters witness reported heavy gunfire in the area near the presidency.
Bana Wagana Ibrahim, a member of Niger's Bureau of the Consultative Council and a deputy in the Alliance of Sahel States (AES) Parliament, said on Facebook that attackers had targeted the military airbase, known as Base 101, but that security forces had regained control.
"Another cowardly attack on Base 101 and once again our defence and security forces ensured ... Situation under control," Ibrahim wrote.
However, a Reuters witness reported further gunfire at the airport and heavy explosions in the pre-dawn hours after Ibrahim's post was published.
As of 7pm AEST, the presidential palace appeared to have been secured by loyalist troops but state television had fallen to the mutineers and the area around the airport was still contested, two security sources and a diplomat said.
Reuters could not independently verify these accounts.
A Niger government spokesperson did not immediately respond to a request for comment.
Niger, a mineral-rich West African nation with significant uranium, oil and gold resources, has been ruled by military officers since the July 2023 coup that ousted President Mohamed Bazoum.
Like its neighbours Burkina Faso and Mali, it has failed to turn the tide in its battle against Islamist insurgencies linked to al-Qaeda and Islamic State despite pledges by military rulers to improve security.
