(Updates toll, adds background)
BAGHDAD, Feb 17 (Reuters) - A series of car bombs exploded in mainly Shi'ite neighbourhoods across the Iraqi capital Baghdad on Sunday, killing at least 20 people and wounding dozens, police and hospital sources said.
The bombs detonated in Sadr City, Habibiya, Qahira, and at least two other districts of the capital.
Bombings have increased since the start of the year with a wave of suicide attacks against Shi'ite targets and security forces as Sunni Islamist insurgents step up their campaign to revive widespread sectarian violence in Iraq.
A suicide bomber killed a top Iraqi army intelligence officer on Saturday after storming his home in a northern town and insurgents set off car bombs in Shi'ite areas across the country at the start of the month, killing 34 people.
No-one claimed responsibility for the weekend attacks but Iraq's al Qaeda affiliate, Islamic State of Iraq, has vowed to take back ground its fighters lost in their long battle with American and Iraqi forces. (Reporting by Kareem Raheem; writing by Patrick Markey)