At least 20 people have been killed and more than 100 others wounded in a series of early morning explosions in cities across Iraq, officials say.

Attacks were reported in Baghdad, as well as Tuz Khurmatu and Kirkuk in the north and Nasariyah in the south.

The co-ordinated attacks occurred during the morning rush hour and mainly involved car bombs.

The violence comes ahead of Iraqs provincial elections on 20 April, the first in the country since 2010.

Mondays attacks were particularly broad in scope, with several cities hit, including Fallujah, Tikrit, Samarra and Hilla.

The explosions were caused by dozen of cars packed with explosives and three roadside bombs, AFP news agency reported.

Three car bombs went off minutes apart in Tuz Khurmatu, killing six people and wounding 60, AFP reported.

A number of attacks were also reported in Baghdad.

In one incident, two car bombs claimed two lives and wounded 17 at a checkpoint at the heavily guarded airport, Reuters reported.

In the northern city of Kirkuk, nine people were killed when six car bombs went off simultaneously, police said.

Three of the bombs exploded in Kirkuks city centre - one in an Arab district, one in a Kurdish area, and a third in a Turkomen district, Associated Press reported.

Other blasts were reported elsewhere in the city, which is home to a mix of ethnic groups with competing claims.

Elsewhere, gunmen armed with pistols fitted with silencers shot and killed a police officer while he was driving his car in the town of Tarmiyah, 30 miles (50 km) north of Baghdad, AP said.

No group has admitted carrying out Mondays attacks.

But they come at a time when tensions are high between Iraqs Sunni and Shia, amid claims by the majority Sunni Muslim communities that they are being marginalised by Prime Minister Nouri Malikis Shia-led government.

Sunni Islamist militants linked to al-Qaeda have attempted to destabilise the government by stepping up attacks, mainly on Shia but also Sunni targets this year.

Although violence has decreased in Iraq since the peak of the insurgency in 2006 and 2007, bombings are still common.