Demonstrators in Niamey converged on the French embassy and set fire to its doors, stoned the building and burned the country's flags.

Russian mercenary group Wagner is already operating in neighbouring Mali and its boss Yevgeny Prigozhin has hailed the coup as good news and offered his fighters' services.

Kremlin chief Vladimir Putin would like to expand his country's influence in the region.

However, it is unclear yet whether the new military leadership is going to shift towards Moscow or seek to stick with Niger's Western allies.

It came as the West African regional bloc ECOWAS meeting at an emergency summit on Sunday gave the mutineers one week to reinstate ousted President Mohamed Bazoum or face sanctions and the possible use of force.

The group warned it would take "all measures necessary" to restore the country's democratically-elected government, while the African Union has also issued its own ultimatum.

Mr Bazoum was elected two years ago in Niger's first peaceful, democratic transfer of power since independence from France.

General Abdourahamane Tiani declared himself new head of state on Friday following the military takeover.

Warning against any military intervention, junta spokesperson Colonel Amadou Abdramane said: "We want to once more remind ECOWAS or any other adventurer of our firm determination to defend our homeland."

The coup in Niger has been widely condemned by neighbours and international partners including the United States, the United Nations, the European Union and France.

They have all refused to recognise the new leaders and have demanded the elected president's return.

Niger is one of the poorest countries in the world, receiving close to $2bn (£1.6bn) a year in official development assistance, according to the World Bank.

It is also a security partner of France and the US, which both use it as a base to fight an Islamist insurgency in West and Central Africa's wider Sahel region.

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Russia will look on Niger coup 'very favourably'

Conflict experts say out of all the countries in the region, Niger has the most at stake if it turns away from the West, given the millions of dollars of military assistance the international community has poured in.

US secretary of state Antony Blinken said the continued security and economic arrangements that Niger has with the US hinged on the release of Mr Bazoum - who remains under house arrest - and "the immediate restoration of the democratic order in Niger".

France has suspended all development aid and other financial aid for Niger.

The Elysee said in a statement said: "Anyone who attacks French nationals, the military, diplomats, or French interests will spur an immediate and uncompromising response from France."

In the UK, the Foreign, Commonwealth and Development Office said in a statement that Britain "condemns in the strongest possible terms attempts to undermine democracy, peace and stability in Niger".

The statement continued: "The Communique agreed at the Fifty First Extraordinary Summit on the Socio-Political Situation in the Republic of Niger, held by ECOWAS on 30 July sets out a strong and clear response to this infringement of the democratic rights of the people of Niger.

"We continue to stand by ECOWAS and their efforts to ensure a return to democracy in Niger."

The coup leaders said they overthrew Mr Bazoum because he was not able to protect the nation from growing jihadi violence.

But some analysts and Nigeriens argue this was just a pretext for a takeover that is more about internal power struggles than the nation's security.

Professor Amad Hassane Boubacar, who teaches at the University of Niamey, said: "Everybody is wondering why this coup? That's because no one was expecting it.

"We couldn't expect a coup in Niger because there's no social, political or security situation that would justify that the military take the power."