Pope Francis has appealed for the release of six Nigerian nuns kidnapped from their convent in the town of Iguoriakhi, Nigeria, last month.

The women – three sisters and three aspirants undergoing training and discernment before taking their vows – were taken by gunmen who entered their house near the river and robbed it, then abducted them using speedboats.

Crux reports that they had been in the area for several days and had engaged in a gun battle with local police.

The bishops' conference said that 'agents of darkness continue to hold our people to ransom through kidnapping, armed robbery and other dehumanizing activities' and that the bishops were 'saddened and pained by the continued detention of our daughters, the Sisters of the Eucharistic Heart of Jesus'.

'We appeal to those holding them to please heed our appeal and immediately release them,' the bishops said.

Pope Francis said on Sunday: 'From the heart, I unite myself to the appeal of the bishops of Nigeria for the liberation of the six Sisters of the Eucharistic Heart of Jesus, kidnapped roughly a month ago from the convent in Iguoriakhi.

'I pray with insistence for them, and for all the other people who find themselves in this painful situation. May they, on the occasion of Christmas, finally return to their homes.'