Officials say the suicide attacker blew himself up among a crowd of mourners at the funeral northeast of Baghdad. At least 36 people were killed and dozens of others were wounded.
At the United Nations, Secretary-General Kofi Annan condemned the attack as a "horrendous crime" against civilians.
Elsewhere in Iraq, a car bomb exploded, killing seven people, and a dozen others died in separate attacks.
Insurgents also attacked a convoy of oil tankers north of the Iraqi capital, destroying at least four of the vehicles.
Meanwhile, a previously unknown group, called the Revenge Brigade claimed responsibility for kidnapping the sister of Interior Minister Bayan Jabor. In an unverified claim, they demanded the release of women prisoners and an end to raids by Interior Ministry forces.