A new wave of bombings has hit Iraq's capital, Baghdad, killing at least 20 and wounding dozens more, Iraqi authorities have said.

Iraqi police say the deadliest in Sunday's attacks took place in Baghdad's northern Shaab neighbourhood, when two parked car bombs exploded simultaneously near a restaurant and a tea house. Officials say that blast killed at least ten people and wounded 26.

Another parked car bomb ripped through in capital's Shia eastern district of Sadr City, killing five and wounding 10, while another explosion killed three civilians and wounded six in a commercial area in the central Bab al-Muadham neighbourhood, officials said.

Two further blasts killed two civilians and wounded 13, police said.

Battle for Fallujah

Elsewhere in Iraq, government forces are preparing a "major attack" to retake rebel-held Fallujah, a senior official said on Sunday.

It means a fresh onslaught for the city, west of Baghdad, which has been in the hands of fighters from Al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL) since Saturday, a senior security official said.

The takeover of Fallujah and parts of Anbar provincial capital Ramadi, farther west, is the first time that militants have exercised such open control in major cities since the height of the bloody insurgency that followed the US-led invasion of 2003.

"Iraqi forces are preparing for a major attack in Fallujah," a senior Iraqi official told AFP.

Special forces have already conducted operations inside the city, the official said.

The regular army has paused on the edge of the city to allow residents time to leave, awaiting orders to launch "the attack to crush the terrorists".

Secretary of State John Kerry said on Sunday that the United States would provide assistance to Iraqi forces in their battle against the group but that it was "their fight".

Kerry said Washington was "very, very concerned" about the resurgence of ISIL but said it was not contemplating any return of US ground troops, after their withdrawal in December 2011.

"We are not obviously contemplating returning, we are not contemplating putting boots on the ground, this is their fight," Kerry told reporters in Jerusalem.

"But we're going to help them in their fight... We are going to do everything that is possible to help them."

On Friday and Saturday, more than 160 people were killed in the worst violence to hit Anbar province in years.

Source: Al Jazeera and agencies