Iraqi police say a truck bomb has exploded in the ethnically-mixed city of Kirkuk, killing at least 80 people and injuring scores more. From northern Iraq, VOA's Margaret Besheer has more.

Iraqi hospital workers wheel a wounded man into a hospital in  Kirkuk, north of Baghdad, 16 July 2007

A suicide bomber driving an explosives-filled truck struck around noon local time in Kirkuk.

The force of the explosion left a 10-meter-deep crater in the street in front of the headquarters of the Patriotic Union of Kurdistan, the political party of Iraqi President Jalal Talabani.

The blast collapsed the roof of the PUK office and cars and shops were burned and damaged.

Kirkuk police chief Brigadier General Jamal Tahir told Iraqiya television that 20 minutes after the truck exploded, a second vehicle tried to enter a cordoned off area, but when it could not, the driver detonated his explosives on the spot.

That explosion, in a market, was not far from the PUK headquarters. Midday is very hot, and the outdoor market was not very busy. The police chief said no one was killed in that blast.

General Tahir says the driver of a third explosives-filled vehicle - a taxi - was stopped and arrested before he set off his cargo. Bomb disposal experts detonated the explosives in a controlled explosion.

But a third blast happened several hours later, when a car bomb exploded in the southern part of Kirkuk. There were several police casualties in that attack.

Tensions have been rising in the ethnically-diverse city as a referendum is due by the end of the year to decide oil-rich Kirkuk's future. The referendum will likely turn the city over to Kurdish control, a step rejected by many of Iraq's Arabs and Turkmen.

Terrorists have also been moving further north as they are squeezed out of Baghdad and other areas where Iraqi and coalition operations are cracking down on al-Qaida in Iraq and other militant groups.

Monday's blast comes nine days after one of the war's worst suicide attacks. More than 160 people were killed and some 250 others injured in a truck bombing in the village of Amrli, about 80 kilometers south of Kirkuk.