Members of the Islamic State of Iraq, al-Qaeda’s front group in the country, have threatened more attacks on Christians after a siege on a Catholic church in Baghdad Sunday left 58 people dead. It was the deadliest attack ever against Iraqi Christians.

The Islamic militants linked the threats to claims that officials of Egypt’s Coptic Church are holding women captive for converting to Islam. The militants said their deadline to release the women had expired. Consequently, they said their fighters would attack Christians wherever they can be reached.

A spokesmen for the militants also said they were giving the Coptic Church 48 hours to release the women. They’ve specifically mentioned two Egyptian women who are married to Coptic priests. Some believe they converted to leave their husbands. Egypt’s Coptic Church bans divorce. The group also demands the release of al-Qaeda-linked prisoners held in Iraq.

Hundreds of members of Iraq’s Christian community gathered Tuesday for a memorial service in Baghdad. One of the officials read a letter from Pope Benedict XVI, conveying the pope’s sympathy with the grieving community.

Catholic experts told Reuters the attack and the threats confirm fears of a mass exodus of Christians from the biblical lands that were raised in the recent Vatican summit on the Middle East.

“As the terrorists themselves say, their purpose is to eliminate the Christian presence from those lands either by physically destroying Christians or by terrorizing them into renouncing the faith or fleeing,” said Father David Jaeger, a Franciscan expert on the Holy Land and the Middle East.

On Tuesday night, Iraq’s Shiite Muslims bore the brunt of violence. A string of 13 attacks struck Baghdad, despite a network of police and army checkpoints and blast walls crisscrossing the capital. The death toll in that violence climbed to 91 people by Wednesday, according to Iraqi police and hospital officials.

Iraqi state TV aired footage Wednesday of Prime Minister Nouri al-Maliki visiting victims of the blasts in Baghdad’s hospitals. The televised bedside calls to civilians were a first for al-Maliki since he took office in 2006. According to Reuters, a spokesman for Iraq’s chamber said Wednesday parliament will meet Monday for speaker elections, potentially breaking an eight-month political deadlock and securing al-Maliki’s reappointment as prime minister.

The Sunni-backed bloc of former Prime Minister Ayad Allawi narrowly defeated al-Maliki’s Shiite-dominated alliance in the March 7 parliamentary election. Neither bloc won an outright majority.

The Associated Press contributed to this report.