Four people were killed and two wounded in gunmen attacks in central Iraq on Thursday, while Iraqi security forces captured three al-Qaida leaders and dozens of suspects, the police said. In Baghdad, gunmen attacked a police checkpoint in the southwestern district of Amil and killed a policeman before they fled the scene, an Interior Ministry source told Xinhua on condition of anonymity. In Iraq\'s western province of Anbar, a policeman was killed and two others wounded when gunmen using assault rifles attacked their checkpoint in southern the provincial capital city of Ramadi, some 110 km west of Baghdad, a source form Anbar\'s operations command anonymously told Xinhua. In Salahudin province in north of Baghdad, Iraqi security forces carried out a pre-dawn raid on a house of a suspected al- Qaida leader in the town of Shirqat, some 110 km north of the provincial capital city of Tikrit, killing the suspect as he tried to escape the scene, a provincial police source told Xinhua on condition of anonymity. Also in Shiqrat, an Iraqi soldier was killed in a roadside bomb explosion near his military vehicle while driving on a road outside the town, the source said. Separately, Iraqi security forces conducted search operations during the past 24 hours in a cluster of villages around Shirqat and arrested some 80 people, some of them wanted for terrorism charges, the source added. Salahudin province, located in northern central Iraq, is a mainly Sunni province. Its capital city of Tikrit, some 170 km north of Baghdad, is the hometown of former president Saddam Hussien. Elsewhere, Iraqi security forces captured two al-Qaida leaders in the city of Mosul, some 400 km north of Baghdad, the Interior Ministry\'s counter-terrorism department said in a statement, including Tha\'ir Salman, known as the explosives expert for Mosul\' s branch of the self-styled Islamic State of Iraq (ISI), the al- Qaida front in the country, and the other is Ahmed Ismail Zouba, al-Qaida\'s religious leader of Mosul. In Iraq\'s northern province of Kirkuk, an Iraqi police force captured Uday Faris, a local al-Qaida leader, during a raid on his hideout in the town of Hawija, southwest of the provincial capital city of Kirkuk, some 250 km north of Baghdad, a local police source said. Faris was one of 14 al-Qaida prisoners who escaped from a prison in Salahudin province in September 2009. Violence and sporadic attacks are still common in the Iraqi cities despite the dramatic decrease of violence over the past few years.