BAGHDAD — The worshipers heard the first shots and explosions about 20 minutes after the beginning of Sunday Mass at Our Lady of Salvation Church.

Heads turned, the sermon stopped abruptly and the Rev. Wassem Sabeeh quietly began ushering parishioners into a fortified room in the rear of the church.

‘We realized these explosions were close,’ said Bassam Sami, 21, one of the survivors of the attack on a Baghdad church carried out by heavily armed suicide bombers that left at least 58 people dead. ‘Father Wassem started pushing people inside the room.’

Once they penetrated the church building, the silent assailants began executing people. ‘They were well trained,’ Sami said. ‘They didn’t say anything. It was like someone had cut out their tongues.’

The carnage that unfolded during the next few hours outraged many in a city that has seen more than its share of bloodshed. The siege suggested that al-Qaeda in Iraq, the weakened Sunni insurgent group that asserted responsibility for the attack, remains capable of carrying out mass-casualty operations.

The target, an Assyrian Christian church in the upscale Karrada neighborhood, was highly unusual. The extremist group has in the past year directed its dwindling resources toward crippling symbols of the Shiite-led Iraqi […]