KIRKUK, Iraq (AP) _ A suicide attacker detonated a car bomb Saturday outside a police academy in the northern Iraqi city of Kirkuk as hundreds of trainees and civilians were leaving for the day, killing at least 20 people and wounding 36, authorities said.
Separately, U.S and Iraqi forces clashed with insurgents in another part of northern Iraq after launching an operation to destroy an alleged militant cell in the town of Tal Afar, the U.S. military said. At least nine people were killed and 50 injured, hospital officials said.
Ambulances raced to the scene of the blast in Kirkuk, where a seven cars were ablaze. Rescue personnel ferried the wounded away on stretchers. Some waited for attention while sprawled on the building's steps.
``This is a terrorist act against members of Iraqi police who were heading to their homes,'' said Kirkuk police Col. Sarhat Qadir.
Iraqi police sealed off roads leading to blast site. Iraqi police fired warning shots into the air to disperse weeping and frustrated people racing to the area to learn the fate of their relatives.
Gen. Torhan Abdul-Rahman Yousif, the director of Kirkuk police, put the death toll at 20, with 36 others wounded.
Militants waging a 16-month-old insurgency in Iraq have used car bombings, sabotage and kidnappings in an effort to destabilize the country and drive out coalition forces and reconstruction workers.
Saturday's bombing was the latest in a string of attacks specifically targeting Iraqis working for the U.S.-backed interim government of Prime Minister Ayad Allawi.
Insurgents see police as collaborators with coalition forces, who are struggling to restore order. Militants have blown up police stations all over the country, gunned down officers in drive-by shootings and battered police stations with mortar barrages and rocket-propelled grenades.
In Tal Afar, about 120 miles northwest of Kirkuk, a U.S. observation Kiowa helicopter was hit by enemy fire and forced to make an emergency landing amid the fighting, said U.S. Army Capt. Angela Bowman. The aircraft's two crew members were wounded, she said.
At least eight people died and another 50 were wounded during clashes in the city, said Fawazi Mohammed, the head of the local hospital. Many of the casualties were caused by when a mortar shell hit in a marketplace, authorities said.
American soldiers killed two insurgents and captured another, while three Iraqi national guardsmen were injured in the fighting, the military said.
A U.S. Stryker Brigade vehicle securing the helicopter's site later came under attack by rocket-propelled grenades, the military said. Troops fought back, killing two attackers.
In response to heavy enemy fire, soldiers on the ground were forced to call for air support and a warplane dropped a bomb near the town, the military said. It wasn't clear if there were any civilian casualties.
U.S. intelligence believes Tal Afar is being used as a haven by insurgents smuggling men and arms into Iraq from nearby Syria. It opted to launch the Saturday operation in a bid to flush them out, the military said.
In Baghdad, meanwhile, several mortar rounds landed near a checkpoint in the Iraqi capital Saturday close to the heavily fortified Green Zone, which houses Iraqi government offices and the U.S. Embassy, a spokeswoman for coalition forces in Baghdad said.
It was not immediately known whether the shells caused any casualties.
The mortar rounds landed near the entrance to the Green Zone's convention center, where members of Iraq's 100-member transitional assembly, known as the Iraqi Council, gathered for a meeting.
Mortar rounds also exploded near the Al-Rashid hotel, not far from the Green Zone, the spokeswoman said.
Also Saturday, saboteurs also blew up an oil pipeline in southern Iraq, the latest attack targeting the country's crucial oil industry, police and oil officials said.
Firefighters struggled to put out the blaze caused by the explosion near Hartha, 19 miles north of Basra, and technicians were forced to shut down the pipeline, said police Maj. Col. Nouri Mohammed.
The pipeline carried 15,000 barrels of crude a day from the Nahran Omar oilfields to an export storage tank called Zubayr-1 in the Faw peninsula and its shutdown is not expected to significantly affect Iraq's overall exports of 1.9 million barrels a day.
Separately, France's interior minister insisted Saturday that signs still point to a release soon for two French journalists held hostage in Iraq but suggested that insecurity there was complicating the process.
``All the indications that we have confirm the hope of a release soon,'' Interior Minister Dominique de Villepin said in Paris. ``But you know the situation that exists in Iraq and, in this context, the greatest caution is of course necessary.''
France's foreign minister said Thursday that he had proof that Christian Chesnot and Georges Malbrunot were alive and one of their employers later said they had been handed over to another, more moderate group that favored their release.
Chesnot and Malbrunot disappeared Aug. 19 as they headed for the southern city of Najaf. A militant group calling itself the ``Islamic Army of Iraq'' said it abducted them and demanded Paris rescind a law banning headscarfs in public schools. The French government refused.
Also Saturday, eight Iraqi civilians were injured when insurgents fired a rocket into a traffic circle in the northwestern city southern Mosul early Saturday, the U.S. military said in a statement. Most of the victims were struck by shrapnel during the attack late Friday and were being treated in a local hospital.
Unidentified gunmen also killed a former senior Baath party official and ex-mayor of the northeastern town of Khan Bani Saad, hospital officials said. AbdelKarim al-Sadoun was killed as he shopped in the nearby city of Baqouba.
Outside of Baqouba, a U.S. mine detection vehicle damaged by roadside bomb, but there were no immediate reports of casualties, the U.S. military said.