Fifteen people were killed and nine others wounded in separate violent incidents in Iraq on Tuesday, police said. In Iraq's eastern province of Diyala, unknown gunmen shot dead seven shepherds, mainly young men, in a rural area near the town of Abu Saida, some 90 km northeast of the Iraqi capital of Baghdad, a provincial police source told Xinhua. Separately, Iraqi security forces carried out a raid on an insurgent hideout in the town of Sa'diyah, some 120 km northeast of Baghdad, killing four suspected al-Qaida militants, including a local leader, the source said. The troops also seized a cache of weapons and explosives at the scene, the source added. Also in the province, the explosive experts defused two car bombs, one of them loaded with 100 kg of explosives and another loaded with 60 kg in the provincial capital city of Baquba, some 60 km northeast of Baghdad, he said. Diyala province, which stretches from the eastern edges of Baghdad to the eastern border of the country, has long been a volatile area since the U.S.-led invasion of Iraq in 2003 despite repeated military operations against militant groups. In northwestern Iraq, three policemen were killed and another was wounded in a roadside bomb explosion near their patrol in the town of Ba'aj, some 120 km west of Nineveh province' capital city of Mosul, which is about 400 km north of Baghdad, a provincial police source told Xinhua. In Baghdad, a civilian was killed and four others were wounded when a roadside bomb went off at a marketplace in Shaab district in the northeastern part of the capital, a police source told Xinhua. In a separate incident, four people were wounded when a roadside bomb ripped through Nahrawan area in eastern Baghdad, the source said. Iraq is witnessing its worst eruption of violence in recent years. According to the UN Assistance Mission for Iraq, 8,109 Iraqis were killed in the country from January to November this year.