Baghdad ? The moderate leader of the largest Sunni bloc in parliament was assassinated Friday after delivering a sermon at a Baghdad mosque, a killing that could set back efforts to reconcile differences between the two Muslim sects before national elections.

Harith al-Obeidi, 47, was an outspoken advocate for prisoners’ rights, one of the most divisive issues in relations between the disaffected Sunni minority and the Shiite-led government.

He was killed a day after colleagues said he called on parliament to summon interior and defense ministry officials to answer allegations of torture in Iraqi jails. Although most detainees are Sunni, al-Obeidi promoted human rights for all Iraqis, even followers of radical Shiite cleric Muqtada al-Sadr.