Four people were killed and eight others injured Wednesday in separate gunfire and bomb attacks in northern and central Iraq, the police said. In Iraq\'s northern province of Nineveh, gunmen using pistols fitted with silencers shot dead Judge Qassem al-Najdi and his driver in eastern the provincial capital city of Mosul, some 400 km north of Baghdad, a source from the provincial operations command told Xinhua on condition of anonymity. In a separate incident, two policemen were wounded when a roadside bomb went off near their patrol in Mosul\'s southern district of Boursa, the source said. In the western province of Anbar, two roadside bomb explosions went off in a quick succession near the Health Office in central the city of Ramadi, some 110 km west of Baghdad, killing a man and a child and wounding five others, a source from Anbar\'s operations command anonymously told Xinhua. The double blasts apparently missed a police patrol which had just passed the scene, the source added. In Baghdad, gunmen using silenced weapons fired on the car of Ahmed Shakir, a Lieutenant Colonel of the Iraqi counter-terrorism office, in Baghdad\'s southern district of Doura, wounding his driver while Shakir himself escaped the attack unharmed, an Interior Ministry source said on condition of anonymity. The attacks are part of a wave of assassinations by militia and gangs against Iraqi security members, officials and civilians. The attackers\' tactics varied from suicide bombings, gunfire by silenced weapons and sticky bombs attached to vehicles.