Two bombs exploded in a mainly Shi'ite Muslim area of Iraq's capital Baghdad on Thursday, killing six people and wounding 17, police and hospital sources said.

One bomb was planted on a parked motorcycle and the other was a roadside device, they said.

The attacks occurred in the impoverished Sadr City neighbourhood in northeast Baghdad.

Iraq is still plagued by a deadly Sunni Muslim insurgency and Shi'ite militias nearly nine years after the U.S.-led invasion that ousted Saddam Hussein.

On Tuesday, members of the Sunni-backed Iraqiya bloc boycotted Iraq's parliament and cabinet, accusing Shi'ite Prime Minister Nuri al-Maliki's bloc of governing alone in a power-sharing coalition that was supposed to ease sectarian tensions.

The political turmoil that has stoked concern of renewed sectarian strife erupted as the last U.S. troops were leaving in mid-December, when Maliki sought the arrest of a Sunni vice president and asked parliament to remove Maliki's Sunni deputy.

Maliki's moves against Vice President Tareq al-Hashemi and Deputy Prime Minister Saleh al-Mutlaq and a spate of bombings that have killed at least 78 people in mainly Shi'ite areas of Baghdad have only deepened the fears.

The inclusion of Iraqiya in the governing coalition was considered crucial to prevent a slide back into the kind of sectarian violence that killed thousands and took Iraq to the brink of civil war in 2006-7.

Many Sunnis have complained of being sidelined in the political process since Saddam was ousted and majority Shi'ites took power.

(Reporting by Kareem Raheem; Writing by Serena Chaudhry; Editing by Ralph Gowling)