BAGHDAD — Sunni insurgents have intensified their campaign against Iraq's military and security forces.

Officials said Iraqi officers have also become the key target of insurgents. On Sunday, Col. Riyad Abdul Karim, deputy commander of one of Baghdad's police departments, was assassinated.

[On Monday, a U.S. Apache AH-64 helicopter crashed north of Baghdad, Middle East Newsline reported. There was no immediate word on casualties, but witnesses said the helicopter was struck by a missile.]

On June 25, a suicide car bombing targeted the motorcade of the Mosul provincial police chief. Four police officers were killed. The senior commander was not in the convoy.

Insurgents also attacked police stations and senior officers in Ramadi, near the Syrian border. At least eight people were killed in one such strike on June 25.

Insurgents have targeted military and police facilities in central and northern Iraq. The insurgents have employed suicide bombers as well as units of up to 100 fighters in attacks that killed dozens of police and soldiers over the weekend. Iraq has 168,500 trained police and soldiers.

The bloodiest attacks took place on Sunday in northern Iraq. The U.S. military said two suicide bombers blew themselves up in separate attacks in which at least 33 people were killed.

The offensive was said to have been directed by Al Qaida's commander in Iraq, Abu Mussib Al Zarqawi. On June 25, Iraqi security forces captured the commander of the Al Qaida-aligned Ansar Al Sunna, Hilal Hussein Al Badrani, near Mosul. Al Badrani was identified as a Saudi national and close to Al Zarqawi.

One insurgency attack targeted an Iraqi military base in Kosuk near Mosul. The other strike was against a police station in the city. Three U.S. soldiers were also killed in separate insurgency attacks in Iraq on Sunday.

A suicide bomber killed 16 people in a parking lot outside the Iraqi army base, U.S. officials said. They said nearly all of the victims were Iraqi civilian employees.

Another 13 police officers and two civilians were killed in the suicide strike at police headquarters in Mosul. Officials said the blast destroyed the two-story building. Al Qaida claimed responsibility for the suicide car bombing.

Officials said insurgents have deployed units of more than 100 fighters to attack Iraqi police and army facilities. Such a force stormed a Baghdad police station in mid-June.

The insurgents have also been preparing huge caches of weapons for mass-casualty strikes in the Baghdad area, officials said. They said Iraqi and U.S. forces have uncovered several insurgency strongholds around the capital, with arsenals that have included mortars, rockets, anti-tank and anti-aircraft missiles, artillery and rocket-propelled grenades.

"A lot of innocent civilians were saved today by getting these terrorists, their weapons and their money," Lt. Col. Clifford Kent, a Task Force Baghdad spokesman, said.

Last week, Iraqi soldiers and police conducted a joint counter-insurgency operation in Baghdad. Officials said Iraqi soldiers from the 1st Battalion, 5th Brigade, 6th Division teamed up with Iraqi police and coalition forces for Operation Safeguard on June 24.

In all, more than 400 Iraqi and coalition forces conducted a cordon-and-knock sweep of about 1,200 apartments in central Baghdad.

Officials said the operation capped an eight-week training program for the Iraqi army's 5th brigade, scheduled to be formally activated on June 29.

In Washington, U.S. officials said the Sunni insurgency could continue for another decade. They said Iraq's military and security forces would require at least two more years until they could face the insurgents without U.S. help.

"We're not going to win against the insurgency," Defense Secretary Donald Rumsfeld said in a television interview. "The Iraqi people are going to win against the insurgency. That insurgency could go on for any number of years. Insurgencies tend to go on five, six, eight, 10, 12 years. Coalition forces, foreign forces are not going to repress that insurgency."