Most of the people being deported are from Comoros, which said it refused to allow a boat carrying deportees to dock.

The operation, called Operation Wuambushu (“Take Back” in the local language), aimed to expel irregular migrants from Mayotte, claiming it would improve living conditions for locals in France’s poorest department.

Some 1,800 members of the French security forces have been deployed for the operation, including hundreds sent from Paris, with young locals and police clashing in the district of Tsoundzou outside the main town of Mamoudzou since Sunday.

AFP journalists reported clashes outside slums in Mayotte’s main city on Tuesday. Barricades of tyres and dustbins lined the road and protesters threw stones at police, who fired tear gas.

A court in Mamoudzou on Tuesday stopped the clearance of one slum located at Koungou near the capital at the last minute, saying the action had no legal foundation and threatened public liberties. The local administration said it would appeal.

Locals feted the court decision stopping the evacuation, which was due early Tuesday.

“I am overjoyed, we went to court and we won,” exulted Mdohoma Hadja, 33, raising her arms to the skies.

Comoros, whose three islands lie to the northwest of Mayotte, said Monday it had not allowed a boat carrying people expelled from Mayotte to dock. Most of the people being deported are Comoran.

It also said it had suspended passenger traffic at a port where those deported usually land.

The plan is for those without papers to be sent back to the Comoran island of Anjouan, 70km (45 miles) away from Mayotte.

“We will not stop the operations … to fight against delinquency and unsanitary housing, with their consequences on illegal immigration,” the most senior Paris-appointed official on Mayotte, Thierry Suquet, told reporters.

He said he hoped to “quickly resume” boat deportations to Anjouan and hoped the standoff would be ended through “dialogue”.

Intense negotiations between Comoros and France in recent weeks had raised the possibility of a last-minute deal.

But Comoros’s leader Azali Assoumani – who has held the rotating presidency of the African Union since February – said he hoped the operation would be abandoned, admitting Moroni did not have “the means to stop the operation through force”.

In 2019, France pledged 150 million euros ($161m) in development aid as part of a deal to tackle human trafficking and ease the repatriation of Comorans from Mayotte.

Roughly half of Mayotte’s roughly 350,000 population is estimated to be foreign, most of them Comoran.

Many Africans, especially Comorans, try to reach Mayotte every year. These risky crossings risk ending in tragedy when the “kwassa kwassa”, small motorised fishing boats used by people smugglers, are shipwrecked.

Mayotte is the fourth island of the Comoros archipelago that France held on to after an initial 1974 referendum, but it is still claimed by Moroni.