"Ahmad Subaih Wais, a senior official at the Ministry of Water Resources, was shot dead by armed men in the southern Baghdad district of Dura as he was going to work," an Interior Ministry official said on Tuesday.
At least 14 civilians were killed when US forces and Iraqi National Guard soldiers battled fighters in the city of Ramadi on Tuesday, a hospital official said.
Munaim Aaftan, the director of Ramadi hospital, said he had been told the fighting took place at a checkpoint on the edge of Ramadi, 110km west of Baghdad.
In Samarra, fighters armed with light machine guns killed the three policemen in separate attacks within an hour in the southern, eastern and central districts, Iraqi journalist Ahmad al-Samarrai told Aljazeera.
At about 10am, police in Samarra, 125km north of Baghdad, imposed a curfew on the city, but lifted it less than an hour later, al-Samarrai said.
Iraqi police patrols were deployed in the city to pursue the attackers, but no arrests had been reported, he added.
Also on Tuesday, a Bulgarian soldier died when his vehicle crashed in a sand storm in Iraq, the Balkan state's Defence Ministry said.
Another soldier was injured, but was in stable condition, a press officer said.
The accident happened while the soldiers were travelling from Kuwait to a base in central Iraq.
Bulgaria has now lost nine soldiers in Iraq, eight in combat, and five civilians.
In Baghdad, a car bomb exploded near a police patrol in the western neighbourhood of Gazaliya, wounding a policeman and a civilian, the same Interior Ministry official said.
Another three bombs went off in the capital, wounding three policemen.
Also in the capital, three Baghdad University students were injured when Iraqi police forces dispersed a protest organised by dozens of students in the university compound in Bab al-Muadham area, Aljazeera has learned.
The demonstration was staged in protest against the killing of a student of the pharmacology college who had organised a ceremony celebrating the announcement of the new Iraqi government.