Baghdad, Iraq ? Suicide bombers ripped through a crowded market and a line of security force recruits Wednesday as a wave of explosions and gunfire across Iraq killed at least 69 people — pushing the death toll from insurgent violence to more than 400 in less than two weeks.

The bloody attacks, which also wounded 160 people, came despite a major U.S. offensive targeting followers of Iraq’s most-wanted terrorist near the Syrian border, a remote region believed to be a staging ground for some of the assaults.

The day’s events underscored how intense the fight for Iraq’s future has become in the scant three months since Iraqis voted in the country’s first democratic elections and more than two years since the United States declared the end of major combat.

Insurgents averaged about 70 attacks a day at the start of May, up from 30-40 in February and March, said Lt. Col. Steven Boylan, a spokesman for U.S. forces in Iraq.

In Saddam Hussein’s hometown of Tikrit, 80 miles north of Baghdad, a suicide car bomb exploded in a small market near a police station, killing at least 33 people and injuring 92, police and hospital officials said. The attacker swerved into a crowd of day laborers waiting to be picked up for work at construction sites after heavy security prevented the vehicle from reaching the station, police said.

Associated Press Television News footage showed charred and mutilated bodies piled up at the Tikrit General Hospital morgue. As yet another body arrived, a man with bloodied trousers sank to the floor and sobbed.

The attack came despite a new regulation barring anyone from driving alone in Tikrit. The rule, announced by local police and officials after a suicide car bombing last week, was designed to make it easier for security forces to spot suicide attackers, who generally act alone.

It was not immediately clear why it did not help prevent Wednesday’s attack. The rule may not have been firmly enforced, or the 7:15 a.m. attack may have happened so early that police were not prepared for it.

The Sunni militant Ansar al-Sunnah Army claimed responsibility for the attack in a posting on its Web site Wednesday. But it differed in the details, denying the attack was carried out by a suicide bomber and saying it was aimed at Iraqis who work in the U.S. base in Tikrit. The claim of responsibility could not be verified.

An Iraqi man sits grieving next to empty coffins outside a hospital Wednesday after a suicide car bomb exploded in a small market in Tikrit, Iraq.

About 90 minutes later, in Hawija, a town 150 miles north of Baghdad, a man with hidden explosives slipped past security guards at a police and army recruitment center and blew himself up outside the building where applicants were lined up. At least 30 people were killed and 35 injured, police said.

“I was standing near the center and all of a sudden it turned into a scene of dead bodies and pools of blood,” police Sgt. Khalaf Abbas said by telephone from the site. “Windows were blown out in nearby houses, leaving the street covered with glass.”

Four more car bombs exploded in Baghdad, including one that wounded three U.S. soldiers, the U.S. military said. In the other three, four Iraqis were killed and 14 wounded, including at least three policemen, Iraqi police said.

In western Baghdad, gunmen clashed with a police patrol on a highway, killing one officer and wounding another.

Another bomb exploded at Iraq’s largest fertilizer plant in the southern city of Basra, killing one person and wounding 23, police and employees said. The blast set fire to a gas pipeline and destroyed about 60 percent of the plant.