The US military has renewed its aerial assault of Falluja amid reports of fierce clashes with the city's resistance, an Iraqi journalist said. According to independent Iraqi journalist Fadhil al-Badrani, US warplanes targeted Falluja's eastern and southern districts. He said fierce clashes had broken out in the city centre between US forces who have been in the city since 8 November and Iraqi fighters who had infiltrated back in across the Euphrates river. "There is no way to determine the number of casualties as US authorities have barred journalists and aid workers from entering Falluja," al-Badrani told Aljazeera. **Falluja return delayed*** The US military had earlier said it could not recommend to the Iraqi interim government the return of residents to Falluja. "At some point we will make a recommendation; we have not reached that point," Lieutenant Colonel Dan Wilson, a deputy commander of the First Marine Expeditionary Force, told reporters in a military base near Falluja late on Friday. The Iraqi interim government had promised on Thursday residents could begin returning to the city, west of Baghdad, as early as next week, saying that basic services and aid had been restored. But US marines, backed by a small Iraqi force, are apparently still engaged in fighting with the city's remaining resistance. There are also fears that some civilians may be trapped. "We know of 150 civilians trapped in the city," al-Badrani said. **Elections staff targeted*** Meanwhile in the capital, witnesses said an armed group fired on a police car as it drove through central Baghdad on Sunday, then dragged three passengers from the vehicle and shot them dead. The vehicle was then set on fire. Witnesses said the people pulled from the car were wearing civilian clothes although they were travelling in a police car. A spokesman for the Electoral Commission, Farid Ayar, said the three were staff members from an Iraqi elections office. The attack occurred in Haifa Street, a major thoroughfare in downtown Baghdad that has become a focal point of attacks. Fighters armed with AK-47 assault rifles and pistols then set up a roadblock on the street, stopping and searching every car that passed, pointing their guns in through the windows, the witnesses said. Some scenes were filmed by Reuters Television. There were no police or US forces in the area. The police source said units were unable to get to the scene. **Second attack*** The attack on elections workers is the second in as many days. On Saturday, two people were killed and eight wounded in a mortar attack on an election office north of Baghdad, police and hospital sources said. They said five mortars landed on the premises in Dujail, one of many around the country providing information to potential voters before the 30 January election. It will be used as a polling station on the day of the vote in six weeks' time. Among the wounded were six Iraqi security personnel, who were guarding the office against attack in the predominantly Sunni town, about 50km north of the capital. **Deadly blasts hit Karbala and Najaf*** Car bombers have struck the twin Iraqi cities of Najaf and Karbala, killing at least 64 people and wounding more than 140 others, six weeks before planned elections. Both bombs, which went off about two hours apart on Sunday, exploded near crowded bus stations in a seemingly coordinated effort. Iraqi medical sources said about 48 Iraqi civilians were killed and another 90 wounded in the car-bombing in Najaf, while the explosion that rocked Karbala killed 16 Iraqis and wounded 56 others, Aljazeera reported. The car bomb blasts were not far from the Imam Ali mosque in Najaf and Imam Hussain mosque in Karbala. In Najaf, the car was detonated about 300 yards from the Imam Ali shrine, near crowds of people queuing for buses and taxis and not far from busy offices. The explosion left stunned crowds waiting in freezing temperatures for ambulances. A thick column of smoke rose from the blast site as rare drizzling rain fell. In Karbala, an official at the main hospital said all the victims appeared to be civilians and there were many women and children among them. Speaking to Aljazeera from the city, Hussain al-Shimri, an Iraqi journalist, said the explosion left body parts scattered everywhere. The impact of the blast was such that the bodies transferred to the main hospital were little more than lumps of flesh. "It was a slaughter," he said. "Families of the injured who gathered outside Karbala general hospital were panic-stricken." According to al-Shimri, the blasts appeared to have targeted civilians since they occurred in residential places where there were no US military posts or Iraqi police stations. The Karbala attack was the second in five days. On Wednesday, a bomb apparently targeting Shia cleric Abd Al-Mahdi al-Karbalai exploded as he was returning to his office after evening prayers at the Imam Hussain shrine. **PHOTO CAPTION*** A small 'Christmas tree' is seen in the foreground as US Marines adjust artillery outside Falluja. (AFP)