Updated

A truck bomb exploded near a Kurdish party office in this northern oil city Thursday, killing five people and wounding 30 in an attack local officials blamed on Islamic extremists linked to Al Qaeda (search). It was the second bombing this week against Iraqis who cooperate with the U.S. occupation.

In Baghdad, an American general said the 12-day "Operation Iron Hammer (search)" offensive against insurgents in the capital had reduced guerrilla attacks in the city by 70 percent.

Brig. Gen. Martin Dempsey, commander of the 1st Armored Division (search), said the campaign will now focus on using intelligence to disrupt rebel strikes. "What I want the enemy to know is that there is no sanctuary in Baghdad," he told reporters.

The powerful 10:30 a.m. explosion in Kirkuk shattered windows and damaged doors at the two-story, yellow-and-green building of the Patriotic Union of Kurdistan. It also blew out windows of a nearby radio-television station.

At about the same time, twin homicide truck bombs in Istanbul, Turkey exploded at a London-based bank and the British consulate -- attacks that coincided with President Bush's visit to London to meet Prime Minister Tony Blair, his closest European ally on Iraq.

Mayor Abdul Rahman Mustapha also described the attack in Kirkuk as a homicide bombing, saying the driver's body had been recovered but not identified. However, police and Kurdish party officials said it was unclear whether the vehicle was abandoned before it exploded.

Jalal Johar, a PUK official, blamed Ansar al-Islam, a militant Kurdish group linked to the Al Qaeda terror network, and its allies -- other Muslim extremist groups and remnants of Saddam Hussein's regime.

"We had information that terrorist Islamic extremist movements, remnants of the former regime, Ansar al-Islam and Arab fighters have planned to attack the Patriotic Union of Kurdistan in Kirkuk," Johar said. "Our information show that there are terrorist Islamic movements in the region other than Ansar al-Islam"

Asked if he believed Al Qaeda was behind the attack, Johar replied: "In my opinion, yes."

The Patriotic Union of Kurdistan is one of two ethnic Kurdish parties that have supported the U.S.-led coalition. Both are represented on the Iraq's U.S.-installed Governing Council. The PUK leader, Jalal Talabani, is now president of the 25-member council.

Bomb attacks are less frequent in the northern Kurdish-controlled areas than in Baghdad or other parts of central and western Iraq dominated by Sunni Muslim Arabs. On Sept. 10, a homicide bomber blew up his vehicle near a U.S. intelligence compound in the northern city of Irbil, killing three people and seriously wounding four American intelligence officers.

The bombing in Kirkuk, 150 miles north of Baghdad, was the second in as many as days against Iraqis who cooperate with the U.S.-led occupation. Late Wednesday, a car bomb exploded outside the Ramadi home of Sheik Amer Ali Suleiman, a tribal leader close to the Americans. Hospital workers in the city, about 60 miles west of Baghdad, said two people were killed.

U.S. officials said the U.S.-backed mayor of Fallujah, a deeply anti-American city west of Baghdad, resigned Thursday after mounting criticism of his performance and ties to the Americans. Last month, Mayor Taha Bedawi fled his office when it was attacked and torched by angry residents.

In Basra, the Assyrian Democratic Movement said its representative on the municipal council, Sargoun Nanou Murado, was abducted Tuesday on his way to work. His body was found Wednesday.

The party, which represents Iraq's Assyrian minority, also is represented on the Governing Council.

The upsurge in attacks on Iraqis has coincided with the U.S. military crackdown against insurgents, which has apparently prompted the insurgents to tone down attacks against soldiers and focus instead on their Iraqi allies.

Coalition officials believe the guerrillas may be stepping up their intimidation campaign to disrupt plans to transfer power to a provisional government by July 1.

Also Thursday, two gunmen opened fire before dawn Thursday outside the new Jordanian Embassy in Baghdad, killing an Iraqi security guard, police said. Iraqi police officer Hatim Abdul-Karim said witnesses told police two attackers opened fire and fled.

The Jordanians moved to the new chancellery after the Aug. 7 car-bombing at their former embassy building killed at least 19 people.

In Samara, north of the capital, U.S. troops killed 10 Iraqis after gunmen attacked a coalition convoy Wednesday, Lt. Col. William MacDonald said. Two of the attackers were killed in the initial exchange. Eight others were killed when gunmen attacked U.S. reinforcements, who returned fire with M-1A1 Abrams tanks and an Apache helicopter, MacDonald said.

Iraqi witnesses said some of the dead were civilians caught in the crossfire.

Insurgents attacked an American base Thursday evening near the town of Khaldiyah, west of the Baghdad, with rocket-propelled grenade and mortar fire, witnesses said. They said U.S. troops opened fire in retaliation but it was not clear if anyone was hurt.