West African leaders have imposed economic and travel sanctions on Niger's military junta, threatening military action if ousted President Mohammed Bazoum is not reinstated within a week.
Leaders from Ecowas, the bloc of West African nations, held an emergency summit in Nigeria on Sunday to discuss last week's coup.
Ecowas gave the junta seven days to reinstate Bazoum, who is being held captive in Niamey by the presidential guards unit.
In a statement, the regional bloc said it would "take all measures necessary to restore constitutional order" if its demands were not met within a week.
"Such measures may include the use of force", the statement said, adding that military chiefs are to meet "immediately" to that effect.
Ahead of the crisis talks, Gen. Abdourahmane Tchiani - who has declared himself Niger's new leader - warned Ecowas and unnamed Western nations against stepping in.
"We once again reiterate to Ecowas or any other adventurer our firm determination to defend our fatherland," he said in a statement read out on television late Saturday.
Ecowas and the eight-member West African Economic and Monetary Union also announced the immediate enforcement of a no-fly zone over Niger, the closure of all land borders with the country, a halt to financial transactions and the freezing of national assets.
Military officials involved in the coup would be banned from travelling and have their assets frozen.
Anti-French protests
On Saturday, France announced it had suspended all development aid and budgetary support to Niger, following similar measures by both the EU and the US.
On Sunday, several thousands of coup supporters protested outside the French embassy in the capital Niamey.
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Images showed fires at the embassy walls and people being loaded into ambulances with bloodied legs.
Some of the protesters chanted "Long live Russia", "Long live Putin" and "Down with France", according to AFP news agency.
France said it would not tolerate any attack on its interests in Niger, and would respond in an "immediate and intractable manner".
The military coup in Niger, which began on Wednesday, has been widely condemned by neighbours and international partners including former colonial power France, the US, UN, African Union and European Union.
They have all refused to recognise the new leaders led by Gen. Tchiani.
But the coup has been welcomed by the leader of Russia's Wagner mercenary group Yevgeny Prigozhin, who described it as a triumph, Reuters news agency reported.
Niger's coup is the third in the Sahel region since Mali in 2021 and Burkina Faso in 2022.
The Mali junta has brought Wagner in to help it fight militant Islamists, having forced France to withdraw its military presence last year.
France then moved its regional military headquarters to Niger, where some 15,000 troops have continued to fight jihadist violence alongside the Nigerien army.
(with newswires)
