Thirty-three people were killed and 36 wounded in separate violent attacks across Iraq on Wednesday ahead of the country's first parliamentary elections since the withdrawal of U.S. troops in late 2011. A soldier and two army recruits were killed and ten other recruits wounded when a suicide bomber blew up his explosive vest near a crowd of young men who gathered to sign up to join the Iraqi army at a recruitment center near the city of Baladruz, just east of Diyala's provincial capital city of Baquba, some 65 km northeast of Baghdad, a provincial police source said. The attack could cause further casualty among the recruits, but the soldier sacrificed himself by putting his arms around the attacker and taking him to detonate his explosives away from the crowd, the source said. In a separate incident, three soldiers were killed by gunmen who attacked their car at a village near the city of Tuz-Khurmato, some 90 km east of Salahudin's provincial capital city of Tikrit, a provincial police source said. Also in Salahudin province, gunmen blew up a crude oil pipeline in al-Fatha area in east of the city of Baiji, some 200 km north of Baghdad, causing large quantity of oil spill into the nearby Tigris River, a provincial police source said. The pipeline carries crude oil produced from Ajil Oilfield in east of the provincial capital city of Tikrit, some 170 km north of Baghdad, to the refinery in Baiji. A huge fire occurred at the scene, while the oil leak caused pollution in Tigris river that forces many water facilities to stop working in the cities to the south of the leak, the source added. In Anbar province, four civilians were killed and seven others injured by airstrikes and artillery shelling on several neighborhoods in the besieged city of Fallujah, some 50 km west of Baghdad, a medical source from the city hospital said. Anbar province has been the scene of fierce clashes that flared up after Iraqi police dismantled an anti-government protest site outside Ramadi in late December last year. Near Baghdad, five people were killed and four wounded when a sticky bomb attached to a minibus was detonated in Abu Ghraib area, some 25 km west of Baghdad, a local police source said. In Baghdad, at least two people were killed and eight others injured when a car bomb was detonated in Karrada district in central the Iraqi capital in the afternoon, a police source said. In Iraq's northern province of Nineveh, a police colonel was shot dead and his son wounded when his house was attacked by gunmen in the city of Qaiyara, some 50 km south of the provincial capital city of Mosul, a police source said. Earlier in the day, Nineveh was the scene of other deadly attacks in which 15 people were killed overnight in separate attacks by insurgents across the province. The deadliest attack occurred late Wednesday when dozens of gunmen attacked an army base in al-Mahallabiyah area in the west of the provincial capital city Mosul, some 400 km north of Baghdad, an army source said. The battle between the attackers and soldiers caused 13 people killed, including five soldiers, and five others wounded, the source added. In a separate incident, a soldier was killed and another wounded when a roadside bomb struck their foot patrol in eastern Mosul, a provincial police source said. Also in Mosul, gunmen broke into a shop and shot dead the owner from Shabak minority, the source said. Shabak people are a Shiite minority group living in Iraq's northern province of Nineveh, particularly around Mosul. The violence came less than two weeks ahead of the landmark parliamentary elections on April 30, the first in the country since the withdrawal of U.S. troops in late 2011.