Baghdad ? Al-Qaida’s front group in Iraq has threatened more attacks on Christians after a siege on a Baghdad church that left 58 people dead, linking the warning to claims that Egypt’s Coptic Church is holding women captive for converting to Islam.

The Islamic State of Iraq, which has claimed responsibility for Sunday’s assault on a Catholic church during Mass in downtown Baghdad, said its deadline for Egypt’s Copts to release the women had expired and its fighters would attack Christians wherever they can be reached.

“We will open upon them the doors of destruction and rivers of blood,” the insurgent group said in a statement posted late Tuesday on militant websites.

The Islamic State of Iraq is an umbrella group that includes al-Qaida in Iraq and other allied Sunni insurgent factions.

It is unclear exactly what led the group to seize on the conversion disputes between Egypt’s Muslims and its minority Christians, although the issue has become a rallying point for hard-line Islamists in Egypt.

In announcing its reasons for Sunday’s attack, the group said it had given the Coptic Church 48 hours to release the women it says had converted to Islam. The group also demanded the release of al-Qaida-linked prisoners held in Iraq.

“All Christian centers, organizations and institutions, leaders and followers are legitimate targets for the mujahedeen (holy warriors) wherever they can reach them,” it said.