Iraq ramped up security Friday for its first elections since US troops withdrew, after 27 people died in a late-night bombing at a Baghdad billiards cafe, the latest in a spike in attacks before the polls.

The attack raises further questions about the credibility of Saturday's provincial elections, with 14 candidates already having been killed and a third of the country's provinces not even voting amid an ongoing political crisis.

The polls are seen as a key test of Iraq's stability and security, and will provide a gauge of Prime Minister Nuri al-Maliki's popularity as he grapples with infighting in his national unity government and months of protests by Iraq's Sunni Arab minority.

The bombing struck at 10:00 pm (1900 GMT) on Thursday in the west Baghdad suburb of Amriyah, leaving 27 dead and more than 50 others wounded, security and medical officials said.

Among the dead were at least three children and a woman.

The blast hit the Dubai cafe, which lies inside a small shopping mall on the main road in the predominantly Sunni neighbourhood that is filled with families, as it contains restaurants and clothes shops.

The cafe itself, however, is mostly frequented by young men playing billiards and video games.

The glass windows of the mall, and of nearby shops and houses, were shattered by the blast, an AFP journalist said, while witnesses reported heavy damage inside the building itself.

Security forces restricted access to the neighbourhood and movement within, with motorists having to pass six checkpoints to enter, but the tightened searches did little to placate anger in Amriyah, where many residents accused authorities of negligence.

"If it was not them (soldiers) who did it, it was their fault," said one resident who declined to be named. "We are surrounded by walls and checkpoints, so if it's not them who did it, they helped because they were lazy or they did not perform the checks well."

"It's their fault."

The bombing is the latest in a wave of violence, with 110 people killed in attacks from Sunday to Thursday, an average of 22 per day, according to AFP figures.

An average of 11 people died in violence per day in the first 18 days of April, the figures show.

And attacks killed more than 200 people in each of the first three months of 2013, compared to significantly lower figures in each of the last three months of 2012.

No group immediately claimed responsibility for the late Thursday attack, but Sunni militants linked to Al-Qaeda frequently carry out bombings in both Sunni and Shiite neighbourhoods across Iraq, in a bid to undermine confidence in the government and security forces.

Officials and diplomats also complain that a long-running spat that has pitted Maliki against several of his erstwhile government partners has been exploited by insurgent groups to enhance their room for manoeuvre on the ground.

An estimated 13.8 million Iraqis are eligible to vote on Saturday for more than 8,000 candidates, with 378 seats being contested.

It is the first vote since March 2010 parliamentary polls, and the first since US forces withdrew from Iraq in December 2011.

Diplomats have raised questions over the credibility of the vote, as attacks against candidates have left at least 14 dead and others withdrawing for fear of being targeted.

Meanwhile six of Iraq's 18 provinces will not be taking part, including two where authorities say security cannot be ensured.

Iraqi forces are solely responsible for polling day security, the first time they have been in charge without support from American or other international forces during elections since dictator Saddam Hussein was toppled in 2003.