BAGHDAD A suicide truck bomb killed 14 policemen and wounded 42 at a police station north of Baghdad on Sunday and U.S. forces were hit by another suicide bomber at a checkpoint south of the capital, officials said.
U.S. military spokesman Lieutenant-Colonel Christopher Garver said some U.S. forces had to be evacuated after the attack on the checkpoint near a major bridge but no other details about the number or nature of casualties were known.
"The checkpoint was damaged by the explosion, as was the bridge," Garver told Reuters.
"The force of the explosion dropped part of the span but it did not fall on anybody," he said.
The blast hit near al-Iskandariya, close to where a suicide truck bomber killed 12 Iraqi soldiers and wounded 30 others in an attack on another checkpoint on Saturday.
To Baghdad's north, police said a police station in the village of Albu-Ajeel in Salahaddin province was largely destroyed. Many police were initially trapped under rubble, including one officer who called for help on his mobile phone.
Among the dead were five officers, including two colonels, police in the nearby provincial capital Tikrit said. More than 30 police were among some 50 people wounded.
Sunni Islamist al Qaeda and other militant groups have stepped up attacks on Iraq's security forces across the country in recent weeks, seeking to undermine a four-month-old U.S.-backed security plan in Baghdad and nearby regions.
The crackdown has driven some militants out of Baghdad into surrounding towns and cities, especially into Diyala province just north of Baghdad but also Salahaddin, where they have launched attacks on civilians and U.S. and Iraqi forces.
The top U.S. general in Iraq, General David Petraeus, said on Sunday the crackdown would only get into full swing in the "next week or so" with the arrival of the last of five additional U.S. brigades that will bring the total number of U.S. reinforcements in Iraq to 28,000.
"June 15 is the time when, no kidding, they are ready to go," Major-General Rick Lynch, commander of Multinational Division-Central, told reporters.
Thousands of U.S. troops have been deployed in Baghdad, leaving their huge bases on the city outskirts to set up combat outposts in neighborhoods in what is seen as a last-ditch bid to curb sectarian violence and avert civil war.
The crackdown is also designed to buy time for Prime Minister Nuri al-Maliki's weak and divided government to meet a series of political targets set by Washington aimed at promoting national reconciliation.
Fiery cleric Moqtada al-Sadr, whose six ministers withdrew from the government in April in protest at Maliki's refusal to set a timetable for the withdrawal of U.S. troops, met revered Grand Ayatollah Ali al-Sistani on Sunday, sources said.
Sistani, the reclusive spiritual leader of Iraq's Shi'ite majority, is the sponsor of the ruling bloc to which Maliki and other Shi'ite political leaders belong. No details about the meeting were available.
Television pictures of the aftermath of the suicide truck bombing in Albu-Ajeel, 175 km (110 miles) north of Baghdad, showed the burned-out hulks of overturned police vehicles and piles of debris and rubble around the police station.
While several police and hospital sources said only one truck bomb was used, another police official said a second vehicle, a car, was also believed to have exploded.
One police official said an officer who was trapped under rubble made a frantic call to the Tikrit police operations room.
"We are under the building, which collapsed on us. We think it was a car bomb," the official quoted the officer as saying.
The outgoing U.S. commander of the U.S.-led effort to train Iraqi soldiers and police, Lieutenant-General Martin Dempsey, said the initial deployment of Iraqi units from outside Baghdad for the operation had been "frankly disastrous".
Dempsey said new measures had since been put in place and that the Iraqi security forces were making great progress in key areas and he expected them to be able to take over control of at least 14 of Iraq's 18 provinces by year's end.
A prerequisite for the withdrawal of U.S. troops is standing up Iraq's security forces, which have been rebuilt from scratch since the U.S.-led invasion in 2003.