At least 33 people have been killed in a new wave of violence across Iraq, including shelling of a market in the Iraqi city of Fallujah, medical sources said.

The worst of Tuesday's bloodshed was concentrated in Fallujah, which has been under the control of anti-government fighters since the beginning of the year.

Shelling in the city killed 18 people and wounded 43 others, according to Ahmed Shami, a doctor at Fallujah hospital.

The army has regularly shelled the city, and attempted multiple ground offensives in a bid to re-take conflict-hit city from fighters.

Human Rights Watch also said last month that authorities had likely violated the laws of war by targeting Fallujah hospital.

Meanwhile, attacks in and around Baghdad killed nine people, the AFP news agency reported.

In Iskandiriyah, armed men killed five people along a main road in the town before fleeing the scene. It was not clear why the victims were targeted.

The town lies in a confessionally-mixed area south of Baghdad dubbed the "Triangle of Death" for its brutal violence in 2006-2007.

In the capital's northern outskirts, two people were killed by mortar fire in Saba al-Bor, while a policeman was shot dead in Tarmiyah.

Further north, attacks in Salaheddin, Nineveh and Kirkuk provinces killed six people, four of them policemen, officials said.

Figures separately compiled by the United Nations and the government in Baghdad showed more than 900 people were killed last month alone.

Officials blame external factors for the rise in bloodshed, particularly the civil war in neighbouring Syria, and insist wide-ranging operations against armed groups are having an impact.

But the violence has continued unabated, with analysts and diplomats saying the Shia-led government needs to do more to reach out to the disaffected Sunni Arab minority to reduce support for militancy.