BAGHDAD: A spate of rush hour car bombs rocked Shia-majority areas of Baghdad Tuesday, killing 21 people in the first major series of attacks to hit the Iraqi capital since elections last month.

The violence, which also wounded more than 60 people, came as officials are tallying votes from April 30 parliamentary polls amid a protracted surge in bloodshed that has left more than 3,300 people dead already this year.

The government has blamed external factors, such as the civil war raging in neighbouring Syria, for the escalating unrest this year.

But analysts and diplomats say the Shia-led authorities must also do more to reach out to the disaffected Sunni minority and undermine support for militancy.

At least eight car bombs went off in predominantly Shia Muslim areas of Baghdad throughout the morning, when the city is typically gridlocked.

Twin car bombs exploded near a traffic police headquarters in the Baladiyat neighbourhood of eastern Baghdad, and blasts also hit Sadr City, Urr, Jamila, Maamal and the central commercial district of Karrada.

No group immediately claimed responsibility for the attacks.

But Sunni militant groups have in the past set off coordinated bombings in the capital and often target the country's Shia majority.

Iraq is suffering its worst violence since the bloody Sunni-Shia sectarian conflict that killed tens of thousands of people in 2006-2007.

Security officials have expressed worry that militants could seek to exploit the vote-counting process and what is expected to be a long period of post-election government formation to set off attacks which could deepen already fragile ties between Iraq's communities.

The authorities have trumpeted wide-ranging operations targeting militants in Iraq's north and west, insisting they are making progress against a variety of militant groups including the powerful Islamic State of Iraq and the Levant.

But anti-government fighters have continued to hold on to Fallujah, a city a short drive from Baghdad, as well as other pockets of territory in western Iraq.