Russian military personnel have entered an airbase in Niger that is hosting American troops, after a decision by Niger’s junta to expel US forces from the country.

The military officers ruling the west African country have told the US to withdraw its nearly 1,000 military personnel, which until a coup last year had been a key partner for Washington’s fight against insurgents who have killed thousands of people and displaced millions more.

A senior US defence official, speaking on condition of anonymity, told Reuters that Russian forces were not mingling with US troops but were using a separate hangar at Airbase 101, which is next to Diori Hamani international airport in Niamey, Niger’s capital.

The move by Russia’s military puts US and Russian troops in close proximity at a time when the countries’ military and diplomatic rivalry is increasingly acrimonious because of the conflict in Ukraine.

It also raises questions about the fate of US installations in the country after a withdrawal.

“[The situation] is not great but in the short term manageable,” the official said.

The Nigerien and Russian embassies in Washington did not immediately respond to a request for comment.

The US and its allies have been forced to move troops out of several African countries after coups that brought to power groups eager to distance themselves from western governments. In addition to the impending departure from Niger, US troops have also left Chad in recent days, while French forces have been kicked out of Mali and Burkina Faso.

At the same time, Russia is seeking to strengthen relations with African countries, pitching Moscow as a friendly country with no colonial baggage in the continent.

Mali, for example, has in recent years become one of Russia’s closest African allies; the Wagner group mercenary force has been deployed there to fight jihadist insurgents.

The US official said Nigerien authorities had told Joe Biden’s administration that about 60 Russian military personnel would be in Niger, but the official could not verify that number.

After the coup, the US military moved some of its forces in Niger from Airbase 101 to Airbase 201 in the city of Agadez. It was not clear what US military equipment remained at Airbase 101.

The US built Airbase 201 in central Niger at a cost of more than $100m. Since 2018 it has been used to target Islamic State and al-Qaida affiliate Jama’at Nusrat al-Islam wal Muslimeen fighters with armed drones.

Washington is concerned about Islamic militants in the Sahel who may be able to expand without the presence of US forces and intelligence capabilities.

Niger’s move to ask for the removal of US troops came after a meeting in Niamey in mid-March, when senior US officials raised concerns including about the expected arrival of Russia forces and reports of Iran seeking raw materials in the country, including uranium.

While the US’s message to Nigerien officials was not an ultimatum, the official said, it was made clear American forces could not be on a base with Russian forces.

“They did not take that well,” the official said.

A two-star US general has been sent to Niger to try to arrange a professional and responsible withdrawal.

While no decisions have been taken on the future of US troops in Niger, the official said the plan was for them to return to US Africa Command’s home bases in Germany.