Iraqi security forces arrested 12 suspected al-Qaeda members on Saturday, including a senior figure in the group, in connection with an attack on a Catholic church in Baghdad, a security official said.
Fifty-two hostages and police were killed when Iraqi forces tried to free more than 100 Catholics taken hostage at the Our Lady of Salvation church during Sunday mass on 1 November.
The attack was the bloodiest against Iraq's Christian minority since the 2003 US-led invasion.
General Ahmed Abu Ragheef, the Interior Ministry's head of internal affairs, said security forces arrested al-Qaeda's Baghdad leader, Huthaifa al-Batawi, and 11 others.
"Iraqi forces have successfully arrested the terrorist group involved in the attack on the church in Baghdad," he said.
Security forces also killed Abu Ammar al-Najadi, a leader of the Islamic State of Iraq (ISI), al Qaeda's local affiliate, and seized 6.5 tonnes of explosives planned for use against a government ministry, hotels and the Christian community, Ragheef said.
ISI claimed responsibility for the church attack.
Iraq's Christians, who once numbered 1.5 million out of a total Iraqi population of about 30 million, have frequently been targeted by militants via church bombings and the assassination of priests. Many have fled.
Days after the Catholic church siege in early November, bombings and mortar attacks targeting Christians killed at least three people and wounded dozens in the capital.