Up to 18 people were killed and 44 wounded in attacks, including a suicide tanker truck bombing, in central and northern Iraq on Tuesday, the police said. In northern Iraq, Iraqi security forces clashed with gunmen during a security operation in the western part of the city of Mosul, some 400 km north of the Iraqi capital of Baghdad, a local police source told Xinhua on condition of anonymity. The clashes resulted in the killing of three security members and four gunmen, the source said, adding that the troops arrested some 15 suspected militants in the area. In Baghdad, a car bomb went off near a minibus carrying passengers in the Shiite Sadr City district in the eastern part of Baghdad, killing up to seven people and wounding 34, an Interior Ministry source anonymously told Xinhua. In a separate incident, a suicide bomber blew up his explosive- laden tanker truck near a police checkpoint in the town of Tarmiyah, some 40 km north of Baghdad, killing a policeman and a civilian and wounding four policemen and four civilians, a local police source told Xinhua. Also in the day, gunmen in two cars attacked a checkpoint manned by members of a government-backed paramilitary group, known as Awakening Council, near the town of Dowr, some 150 km north of Baghdad, killing two of them and wounding two others, a local police source said. The attacks came a day after a wave of deadly car bomb attacks that swept Baghdad that killed at least 34 people and wounded some 155. Violence is still common in Iraq despite a dramatic decrease since its peak in 2006 and 2007, when the country was engulfed in sectarian killings.