The Archbishop of Abuja, Most Rev John Onaiyekan, head of the Christian Association of Nigeria, said the kidnappers had made a "grave mistake".
Father Pius Kii was seized by unidentified gunmen from the steps of his church in Port Harcourt on Sunday.
Many gangs in the Niger Delta make money from kidnapping, extortion and gun running.
Unconfirmed reports from Church sources said militants had demanded a $20,000 (£14,000) ransom for Father Kii.
'Fear God'
"If they can kidnap a priest, then really no-one is safe," Archbishop Onaiyekan said.
"They should realise they have made a grave mistake, fear God and release him."
Father Kii is a member of the Missionary Society of St Paul, a Roman Catholic missionary organisation.
The Movement for the Emancipation of the Niger Delta, the most visible militant group, has not commented on the kidnap.
The group has been kidnapping oil workers since 2006. In the past they have "rescued" non-oil worker hostages from other gangs.
Violence has cut oil production in the Niger Delta by about a fifth.+++++++++++++++++++++++++++++++++++++++++++++++++++
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(Source: BBC)