Two Italian priests and a Canadian nun were kidnapped in northern Cameroon overnight, a bishop and a government source said on Saturday, months after a French priest was seized nearby.
It was not immediately clear who took them, though Nigerian Islamist sect Boko Haram is known to operate in the area.
"Doors were broken towards midnight by unknown people and the religious were taken away. We do not know where they are. The act is not yet claimed but we imagine who is behind this kidnapping," said Bishop Phillippe Stevens, from the parish of Maroua, where the kidnapping took place.
He named the priests as Giampaolo Marta and Gianantonio Allegri, both missionaries sent out by the diocese of Vicenza in northeast Italy, and the nun as Gilberte Bissiere.
Pope Francis was aware of the kidnappings and praying for those taken, the Vatican press office said.
A government source in northern Cameroon said armed forces were attempting to free the hostages, without going into further details.
Allegri had written to his home diocese last month saying local authorities had advised him to travel with a police escort.
"Even if on the surface you do not notice anything in particular that is alarming, it is palpable in our feelings and our conversations," he wrote in the letter dated March 12 posted on the diocesan website.
The priests had been working on improving water supplies and fighting the spread of HIV Aids, as well as their religious duties, the website added.
The Italian Foreign Ministry said it was working with the Italian embassy in Yaounde to resolve the situation.
Boko Haram has killed thousands of people in its fight to carve out an Islamic state in northern Nigeria, which borders the north of Cameroon.
The sect seized a French family of seven on holiday in northern Cameroon in February 2013 and released them in April.
At the time France denied paying a ransom, although a confidential Nigerian government report seen by Reuters said Boko Haram was given the equivalent of $3.15 million by French and Cameroonian negotiators.
The French Catholic priest was captured by an unknown group in the same region in November and freed the following month.