Nigerian rescuers were trying to dig out around 30 miners trapped when an artisanal mining pit collapsed following torrential rains, an emergency official told AFP Wednesday.

Dozens of miners employed by a local mining company were working late Sunday in a huge pit in the village of Galkogo in Shiroro district when it fell in and trapped them, Abdullahi Baba Ara, head of Niger state relief agency said.

"From the information available to us more than 30 miners are trapped in the pit which collapsed on them as they were working inside," Ara said.

"Seven people have been removed with severe injuries while rescue work is ongoing to save the rest," he said.

The exact figure of the trapped miners was not clear and rescue officials were struggling to reach the area due to threats from heavily armed criminal gangs, known locally as bandits.

Minerals like gold, tantalite and lithium are mined in the area.

Rescue operations were also being hampered by limited equipment due to difficult terrain.

"We had planned to deploy to the area, but we were asked not to by security personnel due to the insecure nature of the area as a result of presence of bandits," Ara said.

Shiroro is one of several districts in Niger state terrorised by bandits, who raid remote villages, loot and burn homes as well as kidnap residents for ransom.

Last year, the Niger state government banned mining activities in Shiroro, Munya and Rafi districts due to insecurity and safety concerns.

But artisanal miners ignored the ban and continued to mine to raise money for food and other essentials after bandit raids displaced many from their homes and their farmlands.