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In an Easter message pinned to church bulletin boards around the country, Zimbabwe's Roman Catholic bishops called on President Robert Mugabe to leave office or face "open revolt" from those suffering under his government.

The letter, titled "God Hears the Cries of the Oppressed," was the most critical pastoral message since Zimbabwe won independence from Britain in 1980 and Mugabe assumed leadership of the country for the first time.

Once prosperous, the country is reeling under hyperinflation of more than 1,700 percent, 80 percent unemployment, shortages of food and other basic goods and one of the world's lowest life expectancies.

"As the suffering population becomes more insistent, generating more and more pressure through boycotts, strikes, demonstrations and uprisings, the state responds with ever harsher oppression through arrests, detentions, banning orders, beatings and torture," the Zimbabwe Catholic Bishops Conference said in a pastoral message pinned up at churches throughout the country.

The majority of Zimbabwe's Christians -- including Mugabe -- are Roman Catholics. Several thousand worshippers who packed the cathedral in Harare clustered around the bulletin boards to read the message after morning Mass on Sunday.

"Many people in Zimbabwe are angry, and their anger is now erupting into open revolt in one township after another," the nine bishops wrote.

"In order to avoid further bloodshed and avert a mass uprising, the nation needs a new people-driven constitution that will guide a democratic leadership chosen in free and fair elections," it said.

A similar letter in the nearby nation of Malawi pressured longtime dictator Hastings Kamuzu Banda into holding a referendum on reform in 1992 and calling democratic elections, which he lost, ending 30 years of brutal rule.

"We cannot yet say what the response of our congregations will be, but basic biblical teachings apply. Oppression is not negotiable. It must stop before there can be any dialogue," said the Rev. Oskar Wermter of the Catholic communications secretariat in Harare.

Wermter said the bishops wanted the contents of the letter to receive the widest possible distribution. The letter was delivered in the traditional rural strongholds of Mugabe's ruling ZANU-PF party across the country, where priests showed what he called a very strong interest in it.

In his traditional "Urbi et Orbi" Easter address from the central balcony of St. Peter's Basilica, Pope Benedict XVI singled out Zimbabwe among other troubled countries.

"Zimbabwe is in the grip of a grievous crisis and for this reason the bishops of that country in a recent document indicated prayer and a shared commitment for the common good as the only way forward," the pope said in his Easter message which he read to tens of thousands of faithful in St. Peter's Square,

The bishops called for a day of prayer and fasting April 14 and said there would be a prayer service for Zimbabwe every week after that.

The Anglican church has been more muted, with its leaders generally toeing the ruling party line.

Police violently broke up a multi-denominational prayer meeting March 11, describing it as a banned demonstration. Two pro-democracy activists died and Morgan Tsvangirai, leader of the main opposition Movement for Democratic Change, and a dozen senior colleagues were hospitalized after beatings.

Mugabe subsequently headed off a challenge to his leadership to win party support to stand for another presidential term in national elections in 2008. There was no response from the government Sunday to the pastoral letter and Mugabe was out of the country.