BAGHDAD, Iraq – A suicide bombing ripped through a popular Baghdad kebab restaurant at lunchtime, killing at least 23 people and wounding 36 today as insurgents stepped up attacks nationwide, defying two major U.S.-led offensives aimed at routing foreign fighters.

The U.S. military also announced that a Marine died Saturday during Operation Spear — the first American death reported in the twin offensives.

The bomber detonated a vest laden with explosives at about 2:45 p.m. in the Ibn Zanbour restaurant, just 400 yards from the main gate of the heavily fortified Green Zone and is especially popular with Iraqi police and soldiers.

The explosion killed seven police officers, while the injured included 16 police officers and the bodyguards of Iraqi Finance minister Ali Abdel-Amir Allawi, police Lt. Col. Talal Jumaa said. The minister was not in the restaurant.

Elsewhere, militants staged attacks that killed at least nine people, despite two joint U.S.-Iraqi offensives — operations Spear and Dagger — that began earlier this week with about 1,000 U.S. forces and Iraqi soldiers each.

Insurgents also exploded a water pipeline in the capital, and Mayor Alaa al-Timimi said the city of 5 million people would suffer a 24-hour water shortage.

Nearly 60 insurgents have been killed and 100 captured so far in the offensives, which are aimed at destroying militant networks near the Syrian border and north of Baghdad, the military said. Three Americans have been wounded.

The Marine who was killed Saturday by small-arms fire during Operation Spear had been assigned to Regimental Combat Team 2 of the 2nd Marine Division. At least 1,720 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Troops participating in Operation Spear — in its third day in the Anbar province town of Karabilah — fired Hellfire missiles overnight at two homes where insurgents holed up after shooting mortars at coalition forces, said Lt. Col. Tim Mundy, commander of the 3rd Battalion, 2nd Marine Regiment. The military said they believed four or five militants may have been killed in the counterattack.

A battle tank killed a suspected suicide truck bomber, Marine Capt. Jeffrey Pool said from Ramadi, the provincial capital. The vehicle exploded, and the tank crew observed secondary blasts from explosives rigged to it.

U.S. and Iraqi forces have been shouting through loudspeakers to residents of the western town to leave their homes with white flags and head to a safer area. But most homes already are empty, said Marine Capt. Christopher Goland of Lima Company, a unit of the 3rd Battalion.

Dozens of buildings in Karabilah, 200 miles west of Baghdad, were destroyed after airstrikes and tank shelling, according to an Associated Press reporter at the scene.

Intelligence officials believe Anbar province is a portal used by extremist groups, including Abu Musab al-Zarqawi's al-Qaida in Iraq terrorist group, to smuggle in foreign fighters. Syria is under intense pressure from Washington and Baghdad to tighten control of its porous 380-mile border with Iraq.

The majority of the region's residents are Sunni Arabs, who are believed to make up the core of an insurgency that has killed at least 1,131 people since Prime Minister Ibrahim al-Jaafari's Shiite-led government was announced April 28.

On Saturday, troops searching the town found four Iraqi hostages beaten, handcuffed and chained to a wall in a torture center, the military said. Some of the men were believed to be Iraqi border guards who had been held for three weeks.

Troops searching the bunker found nooses, electrical wire and a bathtub filled with water for electric shocks and mock drownings.

In the basement, troops found automatic rifles, ammunition, terrorist training manuals and DVDs showing insurgents beheading captives, Pool said.

U.S. and Iraqi forces also found a bomb-making factory with blasting caps, cell phones and other materials. They uncovered sniper rifles, ammunition and a mortar system. A nearby schoolhouse believed to be used for training terrorists had instructions for making roadside bombs written on a chalkboard.

The second offensive, Operation Dagger, was launched Saturday, targeting the marshy shores of a lake north of Baghdad. Dagger seeks to eliminate insurgent training camps and weapons caches in the Lake Tharthar area, 50 miles northwest of Baghdad.

Both operations come on the heels of two other major offensives in the same areas that killed about 125 militants earlier this month and in March. Iraqi troops did not participate in earlier offensives in the area.

In other violence, a suicide car bomber killed two Iraqi soldiers and two civilian employees as construction workers were fixing the gate at a security checkpoint in Tikrit, Saddam Hussein's hometown 80 miles north of Baghdad, Army Capt. Muhanad Ahmed said. Eight soldiers and four civilians were wounded in the attack.

A bomb in a car parked near the Shiite al-Nawab mosque also exploded in the northern Baghdad suburb of Kazimiyah, killing one civilian and wounding 27 people, police Maj. Falah al-Muhammadawi said.

Gunmen killed two Iraqi policemen in western Baghdad as they headed to work, while a second band of gunmen killed an electrical engineer going to work at an oil refinery in the capital.

In the northern city of Mosul, two mortar rounds missed the governor's building and landed at a butcher's market, killing a 12-year-old boy and wounding 14 people, hospital officials said.

Also Sunday:

—Saddam Hussein's cousin Ali Hassan al-Majid, better known as "Chemical Ali," was one of eight former regime officials to be shown on a tape released by the Iraqi Special tribunal. The suspects were testifying before an investigating magistrate and signing statements. It was the third such tape released by the tribunal this month.

—The Iraqi government announced it had arrested a suspected member of Abu Musab al-Zarqawi's al-Qaida in Iraq, a man it claimed was responsible for building car bombs and carrying out more than 60 bombings around the capital. Musaab Kasser Abdul Rahman Hassan, known as Abu Younis, was arrested on May 26 during an operation in Baghdad, the government said in a statement.

—The U.S. military said American and Iraqi soldiers had captured six suspected insurgents in raids the day before around central and southern Baghdad — including someone it described as "a specifically identified terror cell financier."