Nigeria's government is making no meaningful effort to rescue more than 250 children abducted from a Catholic boarding school in the central state of Niger last Friday, the main Catholic cleric in the region has told the BBC.

Bishop Bulus Dauwa Yohanna's accusation was disputed by the state's police chief, who accused the school of failing to cooperate with its search and rescue operations.

It is unclear who abducted the children from St Mary's school in Papiri village, but criminal gangs have been involved in kidnappings for ransom across Nigeria.

US President Donald Trump has threatened to intervene militarily in Nigeria if the government fails to stop the killing of Christians.

Nigeria is the most-populous state in Africa, with a large Christian and Muslim population.

Its government says that people of all faiths and no faith are victims of insecurity in the country.

Militant Islamist groups are also waging an insurgency in Nigeria, with the government confirming last week that a senior army general had been killed by jihadists in an ambush in north-eastern Borno state.

The Niger state chapter of the Christian Association of Nigeria (CAN) says that 303 students and 12 members of staff were abducted from the school in Papiri village, but 50 children managed to escape and have been reunited with their families.

Bishop Yohanna - who is the chairman of the Niger chapter of CAN and leads the Catholic church in the region - told the BBC that the only official action taken so far to rescue the students had been to compile their names.

He disputed allegations made by the governor of Niger state, Umar Bago, in local media that the church had defied an order to close its school after threats of attacks.

Meanwhile, Nigeria's police chief Kayode Egbetokun said that he had stepped up operations to ensure the children and members of staff were freed.

The abduction at the school was the third to hit Nigeria in a week, forcing President Bola Tinubu to cancel his trip to the G20 summit to deal with the crisis.