BAGHDAD, Iraq -- Gunmen ambushed a bus full of Iraqis working for the U.S. military, killing 17 civilians and wounding 13 in Tikrit on Sunday, while a car bomb and a gun attack killed four members of the Iraqi security forces elsewhere in northern Iraq.
The violence was the latest in a string of deadly attacks targeting Iraqi forces and others allied with the U.S. military that have killed at least 68 Iraqis since Friday. The surge in bloodshed has come despite major U.S. offensives last month to suppress guerrillas ahead of elections set for Jan. 30.
The gunmen opened fire from two cars at the bus as it dropped off Iraqis employed by coalition forces at a weapons dump in Tikrit, 80 miles north of Baghdad, said Capt. Bill Coppernoll, spokesman for the Tikrit-based U.S. 1st Infantry Division.
Coppernoll said 17 people died and 13 wounded in the attack, which occurred at about 8:30 a.m.
Survivors reported that the gunmen emptied their clips with a spray of gunfire into the bus, then fled, Coppernoll said. The survivors said about seven guerrillas were involved in the attack.
About an hour later, a suicide car bombers drove into an Iraqi National Guard checkpoint in Beiji, about 75 miles to the north, detonating his explosives-packed vehicle, Coppernoll said. Then gunmen opened fire on the position.
Three guardsmen were killed and 18 wounded, Coppernoll said.
Guerrillas also attacked patrolling guardsmen near Samarra, 60 miles north of Baghdad, early Sunday, killing one and wounding four.
Insurgents have routinely targeted Iraqis employed by the U.S.-led coalition and Iraqi security forces, accusing them of collaborating with the U.S.-led occupation forces. The attacks have also taken on a new impetus in the run-up to Jan. 30 elections as insurgents attempt to derail the ballot.
Meanwhile, the Iraqi Red Crescent Society withdrew its relief mission from the battleground city of Fallujah on Sunday at the request of the U.S. military amid concerns over continuing insecurity, the organization's chief said.
Saad Hakki said there had been recent skirmishes near the Red Crescent's base in the city, 40 miles west of Baghdad.
The U.S. military launched a massive offensive to break the guerrillas' hold on Fallujah last month. While most of the city is under military control, U.S. and Iraqi troops have been fighting holdouts for weeks.
It was not immediately clear what effect the Red Crescent's withdrawal will have on Fallujah, a city of about 300,000 people, most of whom fled before the U.S.-led military operation started.
Many Iraqis have complained that the military onslaught against the city destroyed infrastructure and led to a deteriorated humanitarian situation in the city. Some 1,500 protesting Fallujah residents displaced by the fighting demanded Sunday that the government return them to their homes.
Officials had hoped the Fallujah assault would put the rebels on the defensive throughout Iraq. But the latest attacks showed they remain capable of hitting where they choose.
The U.S. commander in Iraq, Gen. John Abizaid, acknowledged that the insurgency is proving a tough task for the country's fledgling security forces, which he said were not yet up to the task of ensuring secure elections, requiring the planned increase in U.S. troops from 138,000 to 150,000.
U.N. special envoy Lakhdar Brahimi warned that credible elections cannot be held Jan. 30 under current conditions.
About 40 small, mostly Sunni political parties met Sunday to demand the elections be postponed by six months, but stopped short of calling for a boycott.
"This means a council will emerge that does not represent all and thus will lack legitimacy," the leaders said in a statement released after the meeting held in Baghdad. Their call echoed concerns expressed previously by Iraq's most influential Sunni politicians that the raging insurgency has made huge areas of the country too dangerous for the polls.
President Bush, Iraqi Prime Minister Ayad Allawi and Iraq's Sunni president, Ghazi al-Yawer, have insisted the vote will be held as scheduled.
Insurgents also pursued their deadly campaign against American troops and Iraqi security forces. Two U.S. soldiers were killed by roadside bombs in Baghdad and near Baqouba Saturday, and two other American soldiers with Task Force Olympia were killed and four wounded when their patrol came under attack in the turbulent northern city of Mosul.
The two soldiers were killed during a patrol in Mosul's Palestine neighborhood Saturday, when they came under fire from insurgents shooting from two mosques and other buildings in the area, according to spokeswoman Capt. Angela Bowman. The U.S. military later returned to the area and detained three suspects.
The killings brought to at least 1,271 the number of U.S. troops to have died since the war began in March 2003, according to an Associated Press count.
The U.S. military also announced that 64 suspected insurgents had been arrested on Saturday in Avgani, a town west of Mosul, a city which has been the scene of increased fighting as insurgents.
A suicide car bomber in Mosul killed seven Kurdish militiamen Saturday belonging to the Patriotic Union of Kurdistan, one of Iraq's two largest Kurdish groups. Two bystanders also died.
In nearby Hawija, gunmen assassinated an official of the Kurdish party, Jalal Dawood, after knocking at the door of his house and shooting him in a hail of gunfire.
Along with Iraq's majority Shiites, Kurdish political parties back the upcoming elections.
Mortars rounds fired toward a U.S. military base in Ramadi, west of Baghdad, missed their mark Sunday and landed on a residential area, killing an Iraqi woman and a child, hospital officials said.
Meanwhile, the militant group Jaish Mohammed, Arabic for Muhammad Army, issued a statement saying its fighters were lying low for "a few days" ahead of an imminent resumption of attacks against U.S. forces.
The group's statement, which could not be immediately verified, also threatened Iraqis against aiding coalition forces that they would be attacked with similar fury as that directed against the U.S. military.