Two Italian priests and a Canadian nun kidnapped in northern Cameroon in early April by suspected Boko Haram gunmen have been released, Cameroon's communications minister said on Sunday.

Church authorities identified the priests at the time of their abduction as Giampaolo Marta and Gianantonio Allegri, missionaries from the diocese of Vicenza in northeast Italy, and the nun as Gilberte Bissiere.

"I confirm the release of the two priests and the nun abducted a few weeks ago. They are in good health. They are now in a plane heading to Yaounde," Communications Minister Issa Tchiroma Bakary told Reuters by phone.

Vatican spokesman Father Federico Lombardi said news of the release "fills us with joy".

"We thank the Lord that this dramatic episode has reached a positive outcome," Lombardi said. Pope Francis had followed the affair closely, he said, and had been informed immediately of the releases.

The priests had been working on improving water supplies and fighting the spread of HIV Aids, as well as their religious duties, according to their diocese website.

One of the priests said in a letter to his diocese - posted on its website - that local authorities had advised him to travel with a police escort due to the deteriorating security situation in northern Cameroon.

Boko Haram fighters have killed thousands of people in the group's fight to carve out an Islamic state in neighbouring northern Nigeria.

They have increasingly carried out attacks and kidnappings in northern Cameroon, including the abduction of a French family of seven in February 2013. The family was released two months later.

A French Catholic priest was captured by an unknown group in the same region in November and freed the following month.

Nigeria's head of counter terrorism in an interview with Reuters on Friday accused Cameroon of failing to make a serious effort to drive Boko Haram insurgents from its territory.

A recent picture of Canadian nun Gilberte Bussier, who was seized by suspected Boko Haram

This file picture taken in January 2014 shows Italian priests Giampaolo Marta (right) and Gianantonio Alllegri (left) flanking Vicenza Bishop Beniamino Pizziol (2nd right) and a local resident in Jericho, near Maroua in northern Cameroon