ABUJA - West African leaders were weighing their next moves on Saturday as they seek to overturn a military coup in Niger that has rocked the region but also triggered a groundswell of support in the country.

Niger's military last month imprisoned President Mohamed Bazoum and assumed power, drawing condemnation from international powers and raising the spectre of further conflict in the impoverished Sahel region of West Africa which is already overrun by a deadly Islamist insurgency.

The regional bloc ECOWAS on Thursday decided to activate a task force drawing on troops from across the region for a possible military intervention to undo what was the seventh coup in West and Central Africa in three years.

At stake is not just the fate of Niger - a major uranium producer and key Western ally in the fight against the Islamists - but also the concerns of global powers with key strategic interests in the semi-desert zone.

U.S., French, German and Italian troops are stationed in Niger to repel local affiliates of al Qaeda and Islamic State that have killed thousands and displaced millions across the Sahel.

Western powers fear Russian influence could grow stronger if the junta in Niger follows Mali's example by ejecting Western troops and inviting in mercenaries from Russia's Wagner Group.

Thousands of people gathered in Niger's capital on Friday to demonstrate in favour of the coup. The rally began at a French military base in the capital Niamey, then protesters with signs and flags spread onto surrounding streets.

"Long live Russia," one protester's sign read. "Down with France.... Down with ECOWAS," referring to the Economic Community of West African States.

Regional army chiefs were set to meet in the coming days. It was not yet clear how long the ECOWAS force would take to assemble, how big it would be and if it would actually invade. The organisation stressed that all options were on the table and it hoped for a peaceful resolution.

Security analysts said the force could take weeks to set up, potentially leaving room for negotiations.

Meanwhile, the African Union, the European Union, the United States and the United Nations all said they were increasingly worried about Bazoum's detention conditions.

The U.N. Commissioner for Human Rights Volker Turk on Friday said the conditions were "rapidly deteriorating" and could amount to a violation of international human rights law.