BAGHDAD — At least 12 Iraqis were killed Sunday in a spate of attacks, many of them in provinces where much-lauded Iraqi-led security operations had taken place recently.

The deadliest attack was in the town of Khalis in Diyala Province, northeast of Baghdad. Five civilians were killed and 10 were wounded when a bomb was detonated in the path of a car carrying the district's top two political and military officials, according to a provincial security official.

The two officials, Uday al-Khadran, the district commissioner, and Lt. Col. Nihad al-Saadi, were wounded in the attack, the sixth attempt on Mr. Khadran's life since he took office in 2004.

Mr. Khadran is a prominent leader in the Islamic Supreme Council of Iraq, a major Shiite political party. He has lost 40 members of his family to attacks since the start of the war in 2003. There is deep resentment of the Shiites' power in Diyala, where the majority of the population is Sunni.

The attack in Khalis on Sunday took place in a part of town where security had been relaxed after a major Iraqi-led security operation across Diyala in July.

A roadside bomb killed one person in Baquba, the provincial security official said.

Saja Qadouri, a member of the Diyala provincial council, blamed laxity and infiltration in the ranks of local security forces for the attack. She said there was little effort to follow through and consolidate the security gains made over the summer.

A similar dynamic appears to be at play in Nineveh Province, according to several Iraqi and American officials interviewed last month. In the provincial capital, Mosul, on Monday, three Iraqi soldiers were killed and four were wounded when their convoy hit a roadside bomb, according to an Iraqi Army official.

Later, one person was killed when a suicide car bomber blew himself up in the path of a police patrol, according to the police chief, Brig. Gen. Abdul-Karim al-Jubouri. Another person was killed by second roadside bomb.

The attacks in Mosul came a day after Iraq's defense minister, Abdul-Kader Jassem al-Obeidi, visited the city and declared that he was "satisfied with the security operations under way."

In Anbar Province, a female suicide bomber struck a hospital on the outskirts of Falluja, killing a woman, according to the provincial police chief, Maj. Gen. Tariq al-Youssef.

The attack came one day after six Iraqis were killed, according to a revised toll provided by General Youssef, in a suicide car bombing at a checkpoint outside the provincial capital, Ramadi.