Iraqi officials say a suicide bombing in a Sunni neighborhood of Baghdad has killed 15 people and wounded about 30 others.

Officials say the bomber attacked a checkpoint in Adhamiya district manned by security volunteers who have turned against al-Qaida. The blast killed a leader of the U.S.-backed militia, Faruq al-Obeidi and six of his bodyguards. Several civilians also were killed.

The attack came as hundreds of thousands of Iraqi Shi'ites returned home from an annual religious festival in the city of Karbala.

At least 30 pilgrims have been killed in attacks since Thursday. But Iraqi officials say the festival concluded Saturday without the major violence that marred the event last year, when deadly gun battles erupted between police and Shi'ite militias.

The pilgrimage marks the birth of Imam al-Mahdi, Shi'ite Islam's 12th and last imam who disappeared in the ninth century.

Meanwhile, the U.S. military says Iraqi and U.S. troops in Diyala province have found an increasing number of roadside bombs and houses rigged with explosives. The military says the bombs are designed to slow the advance of coalition forces into militant havens.

Also, the U.S. military says coalition forces detained eight suspected militants in separate operations in central and northern Iraq on Sunday. It says the troops were targeting al-Qaida operatives suspected of bringing foreigners into Iraq to coordinate bombings.

Some information for this report was provided by AFP, AP and Reuters.