At least 16 people have been killed in a series of bomb attacks in Iraq's northern city of Kirkuk.

The attacks came a day after al-Qaeda named a successor to its Iraq leader, Abu Musab al-Zarqawi, and vowed to take revenge for his killing.

PM Nouri Maliki has launched a security crackdown in Baghdad to try to build momentum following Zarqawi's death.

Kirkuk is home to Kurds, Arabs and Turkmens who claim ownership of the city and the oil-rich lands around it.

The first bombing is believed to have taken place at about 0730 (0330 GMT).

Two policemen and eight civilians were killed, military spokesman Brig Gen Sarhat Qadir told the Associated Press news agency.

About 30 minutes later, a suspected suicide car bomber tried to ram the main police headquarters. Two policemen and three civilians were killed, Gen Qadir said.

The offices of Iraqi President Jalal Talabani's Kurdish PUK party were also targeted. Police opened fire on a suspected suicide car bomber, causing the vehicle to explode.

In another attack, a district police chief was wounded and his bodyguard killed in a bomb attack. A further bomb went off as people gathered at the scene.

The BBC's Andrew North says the concern is that these attacks are part of the revenge promised by al-Qaeda in Iraq for the death of Zarqawi.

The fear is that it will sow discord in an already sensitive part of the country, our correspondent adds.

In other violence, a university professor has been shot dead in Baghdad and at least six bodies were found in different parts of the capital, showing gunshot wounds and signs of torture

Vehicle ban

Mr Maliki has revealed some details of his plan to provide more security for Baghdad's six million residents, which he says will be formally announced later in the week.

Roads into and out of the capital will be secured, people will be banned from carrying weapons and a 2100-0600 curfew will be imposed, he said.

Maj Gen Mahdi al-Gharrawi, commander of public order forces at the interior ministry, told AP that 75,000 Iraqi and coalition forces would be deployed in the capital.

A single uniform would be introduced to identify legitimate forces, he said.

There will be a ban on all vehicle traffic in Baghdad on Fridays between 1100 and 1500 to try to curb attacks during Friday prayers.

Photo Caption

A civilian wounded in a car bombing in Kirkuk is rushed to an ambulance