BAGHDAD (AFP) - A series of car bombs near Shi'ite mosques targeting worshippers attending weekly prayers killed at least 15 people on Friday, the latest in a spike in unrest ahead of Iraq's first polls since 2010.

The blasts, which also wounded 95 people, struck within an hour of each other in the Baghdad neighbourhoods of Binook, Qahira, Zafraniyah and Jihad, as well as in an area of southern Kirkuk city.

No group immediately claimed responsibility for the attacks, but Sunni militants linked to Al-Qaeda frequently target Shiite Muslims whom they regard as apostates and supporters of the Shi'ite-led government.

In Baghdad, four car bombs were detonated near Shi'ite mosques in the east and west of the capital, leaving at least 12 people dead and 25 wounded, security and medical officials said, speaking on condition of anonymity.

And in Kirkuk, which lies 240km north of the capital, three people died and 70 were hurt by another car bomb targeting a Shi'ite mosque, provincial health chief Sadiq Omar Rasul said.

Security forces threatened to detain AFP journalists for attempting to film video and take photographs of the aftermath of the violence in Baghdad.

The attacks come amid a spike in violence nation wide as the country prepares for its first elections in three years - provincial polls that will be held in 12 of Iraq's 18 provinces on April 20.

Questions have been raised over the credibility of those polls as elections have been postponed in two provinces roiled by months of protests, and at least 11 candidates have been killed.

The polls are seen as a key barometer of support for Prime Minister Nouri al-Maliki as he grapples with criticism from within his unity cabinet and months of protests in the minority Sunni Arab community.

And the attack in Kirkuk is also likely to raise tensions in a city at the heart of a long-running dispute over territory between the central government in Baghdad and the country's autonomous Kurdistan region.

The dispute is often cited by officials and diplomats as the biggest long-term threat to Iraq's stability.

Violence is down from its peak in 2006 and 2007 but attacks remain common, and this month's death toll of 256 is already the highest since August, according to figures compiled by AFP.