A car bomb near pet and vegetable markets in Baghdad killed 15 people and wounded another 40 on Wednesday, Iraqi security and medical officials said.

Several cars were damaged in the attack. Hours earlier, a suicide bomber drove his explosives-laden car into a police checkpoint on a highway just south of Baghdad, killing four civilians and three policemen, a police officer and a medical official said. They said 24 people were wounded in the explosion.

All officials spoke on condition of anonymity because they were not authorized to speak with reporters.

The United Nations said Wednesday that at least 1,119 Iraqis died in violence in September. But the real number was likely much higher since the U.N. figure did not include killings in areas controlled by the Islamic State group.

The Sunni extremist group seized around a third of the country in a lightning offensive over the summer, plunging Iraq into its worst crisis since the last U.S. troops withdrew at the end of 2011.

The onslaught by the Islamic State fighters stunned Iraq's U.S.-trained army and security forces, which melted away as the extremists advanced and captured key cities and towns. The militants have also targeted Iraq's religious minorities, including Christians and others, killing hundreds and forcing hundreds of thousands to leave their homes.

The extremist group now controls a large swath of land stretching from northern Syria to the outskirts of Baghdad. It has declared an Islamic state in the areas under its control and imposed a harsh version of Shariah law.

The U.S. began launching airstrikes against the group in Iraq in early August and expanded the campaign to Syria last week. Western nations have contributed to the battle in Iraq, while five Arab states have signed onto the coalition striking the Islamic State group in Syria.

The U.N. mission in Baghdad has little or no access to the areas engulfed in the fighting. The figures released Wednesday in the mission's monthly report were the "absolute minimum" number of casualties and do not include deaths in the western Anbar province or much of northern Iraq, the U.N. said.

The September death toll included 854 civilians and 265 members of the Iraqi security forces. Another 1,946 Iraqis were wounded last month, the U.N. said. The worst-hit city was Baghdad, with 352 civilians killed, it said.

The August death toll stood at 1,420. In June, 2,400 were killed as the Islamic State fighters launched their blitz. It was the highest figure since at least April 2005.

On Tuesday, militants unleashed a series of bombings and other attacks mainly targeting Shiite areas across Iraq and killing at least 47 people, including more than 20 in Baghdad, officials said.

No one claimed responsibility for the latest attacks, which were likely carried out by Sunni militants. The Islamic State group has claimed similar attacks in the past.