A total of 39 persons were killed and some 40 wounded on Sunday in two bombings and gunfire attacks in Iraqi province of Salahudin, officials here said.A barrel filled with explosives detonated near a bridge on early Sunday in provincial capital city of Tikrit in Shishin area, some 170 km from Baghdad, killing 13 persons and injuring 30 others, the source told Xinhua news agency on condition of anonymity.In another incident, an explosive-laden car went off at a parking lot in Iraq's Samarra city, 120 km from Baghdad, leaving 10 persons killed and 10 others injured, an official said.The blast set fire to several nearby cars and caused damages to many others at the scene, the source added.Early in the day, gunmen, believed to be affiliated to Islamic State (IS) militant group, broke into the house of a tribal leader in Tulul al-Baj area, some 50 km north of Tikrit, and opened fire in the house and killed 16 persons, the source said.Terrorist acts, violence and armed conflicts killed 1,792 Iraqis and injured 1,358 others in October across Iraq, the United Nations Assistance Mission for Iraq said.Many blame the current chronic instability, cycle of violence, and the emergence of extremist groups, such as the IS, on the US, which invaded and occupied Iraq in March 2003.