Eighteen people were killed and 14 others wounded Wednesday in bomb attacks and gunfire across Iraq, shaping a setback of Iraq's security after Washington declared the end of combat operations in the country two weeks ago.

In the early hours of the day, a joint U.S. and Iraqi force raided three houses in the city of Fallujah in the western Anbar province at about 2:00 a.m. local time (2300 GMT on Tuesday), killing eight people and wounding four others, a local police source told Xinhua on condition of anonymity.

The raid targeted the house of Yassin Kassar, a lieutenant colonel in former president Saddam Hussein's army, in the neighborhood of Jubail, some 50 km west of Baghdad, the source said.

U.S. and Iraqi soldiers stormed Kassar's house and two neighboring houses, killing eight people, including Kassar and a 75 years old woman, and wounding four others, the source added.

The joint force withdrew from the targeted houses and took four bodies with them, and the Iraqi local police took the other bodies to the morgue.

Meanwhile, the source denied media reports earlier in the day which said that there was gun battle between the troops and gunmen inside the houses during the raid, saying "there was no resistance at all."

The U.S. military confirmed the raid in Fallujah and said that an investigation would be started, without giving further details about the incident.

Local authorities of the city and Anbar province said they were unaware of the raid.

Ahmed al-Dulaimi, a member of Fallujah City Council, told reporters that the council had announced a three-day mourning as of Wednesday in the city in protest of the "massacre perpetrated by special joint U.S.-Iraqi force."

Mohammed Fathi, a member of Anbar's Provincial Council, said the council had held an emergency meeting and called on the outgoing government in Baghdad "to launch a probe into the raid and to apologize to the families of the victims."

Later in the day, Fathi said that after a phone call between Prime Minister Nuri al-Maliki and Qassim al-Fahdawi, governor of Anbar, Maliki positively responded to the call of the provincial council and promised to launch an investigation into the incident.

"Maliki will launch a probe in the raid and has promised to summon the commanders of the Iraqi army and police forces in the province to review the security situation in the province," Fathi said.

The deadly raid in Fallujah came two weeks after U.S. President Barack Obama declared the conclusion of U.S. troops' combat operations in Iraq, but nearly 50,000 soldiers remain in the country with missions of training and supporting Iraqi security forces, along with conducting joint counter-terrorism operations.

Also in Anbar province, an old man was killed and four of his family members wounded in a bomb explosion in their house in the al-Haswah area, near the city of Fallujah, a local police source told Xinhua on condition of anonymity.