Christian religious freedom charity Open Doors is pleading with Nigerian authorities to "breach the cycle of violence" in the country after 50 people were killed in a massacre at a church on Pentecost Sunday.
The priest and an unknown number of worshippers were abducted during the attack on St Francis Xavier Catholic Church in Owo, Ondo state.
Gunmen opened fire on members of the congregation as they gathered to celebrate Pentecost, one of the most important dates in the Christian calendar.
Eyewitnesses said that the attackers also detonated explosives.
Matteo Bruni, the Director of the Holy See Press Office, said that the Pope "prays for the victims and for the country, painfully attacked at a time of celebration, and he entrusts everyone to the Lord, that God might send His Spirit to console them".
Rev Augustine Ikwu, spokesman for the Diocese of Ondo, said that the attack had "left the community devastated".
He added: "We turn to God to console the families of those whose lives were lost."
No one has claimed responsibility for the attack but Open Doors is investigating claims by locals that it was perpetrated by radicalised Fulani herdsmen.
Ondo state lawmaker Adeyemi Olayemi told the Guardian that the attack may have been in retaliation for recent state-imposed restrictions on grazing in Ondo after an upsurge in kidnappings in the state.
"We have enjoyed improved security since herdsmen were driven away from our forests by this administration," said Olayemi.
"This is a reprisal attack to send a diabolical message to the governor."
The attack comes just days after the abduction of the head of the Methodist Church in Nigeria, Samuel Kanu. He was freed after paying a $240,000 (£190,000) ransom.
Open Doors expressed concern that the church massacre occurred in the largely Christian state of Ondo in south-western Nigeria.
Until now, many of the attacks and abductions by Islamist extremists have been carried out in the mostly Muslim north-east.
Open Doors said it was concerned that the violence is now spreading across Nigeria.
Open Doors' spokesperson for the work in sub-Saharan Africa, Jo Newhouse, called for government action to hold the perpetrators to account.
"We condemn in the strongest terms possible the attack on Christians as they gathered in peace to worship God," she said.
"We call on the Nigerian government to adequately discharge its legal obligation of duty to protect its citizens, both under international and domestic legal regimes.
"We also call upon the authorities to take a strong stance against all violence, including Fulani militant violence, investigate the perpetrators, hold them accountable to the justice system and break the cycle of violence that is expanding to other areas of the country, as is clearly shown by this incident.
"The longer these acts go unpunished, the longer they will continue."