A wave of attacks targeting both Iraqi security forces and civilians killed 48 people on Monday, in a second day of deadly violence ahead of the first anniversary of the withdrawal of US forces.

Monday was the deadliest day in Iraq since November 29, when 50 people were killed. The latest violence comes after attacks killed 19 people and wounded 77 on Sunday.

US military forces completed their withdrawal from Iraq on December 18, 2011, ending a nearly nine-year war that cost the lives of tens of thousands of Iraqis, thousands of Americans and hundreds of billions of dollars.

Violence in Iraq is down significantly from its peak in 2006 and 2007, but while Iraqi forces have held their own since the US departure, insurgent groups still pose a significant threat, and attacks occur almost daily.

In the deadliest attack on Monday, a car bomb exploded at a car dealership in north Baghdad, killing at least 11 people and wounding at least 40, security and medical officials said.

In the Karrada area in central Baghdad, a car bomb killed at least one person and wounded at least four, an interior ministry official and a medical source said.

"The security situation is worsening," said Duniyah, a 23-year-old employee of a hotel near the site of the explosion, who was watching the street from inside the hotel entrance, which was strewn with broken glass.

Gunmen attacked a police checkpoint on the highway west of Tikrit, then abandoned and detonated their explosives-rigged car when a patrol pursued them, killing a total of five police and wounding five, a senior police officer and a doctor said.

In the village of Al-Buslaibi, north of Baghdad, a roadside bomb targeting an army patrol killed three soldiers, while an attack by gunmen on army checkpoints in the north Iraqi city of Mosul killed three soldiers, officers and a doctor said.

A car bomb in Khaznah, a village near Mosul populated by the small Shabak minority, killed seven people and wounded 12, while two car bombs near a Shiite place of worship killed five and wounded 26 in the northern flashpoint town of Tuz Khurmatu, security and medical sources said.

Three roadside bombs exploded near Baquba, north of Baghdad, killing one person and wounding four others, while a magnetic "sticky bomb" and a shooting in the city killed two people, police and medics said.

In other attacks in Diyala province, gunmen wounded three Kurds in Jalawla, while a sticky bomb killed two Kurds in Baladruz, according to the same sources.

Khaznah, Tuz Khurmatu and Jalawla are all part of areas which Iraq's autonomous Kurdistan region in the north wants to incorporate, over Baghdad's strong objections.

"The attacks in the disputed internal areas further aggravate the tensions there," UN Iraq envoy Martin Kobler said in a statement condemning the violence, calling for efforts to de-escalate tensions in such areas.

A salvo of 10 mortar rounds slammed into the town of Rutba in Anbar province, killing two and wounding nine, officials said, and a car bomb near Dujail north of Baghdad killed one Iraqi and wounded at least 10 Iranian pilgrims.

A roadside bomb against a police patrol in Madain, south of Baghdad, wounded three police and two civilians, while an attack by gunmen on a Sahwa anti-Qaeda militia checkpoint west of the north Iraq city of Kirkuk killed one militiaman, security and medical officials said.

And a car bomb in Khaldiya, west of Baghdad, killed two civilians and two police, and wounded seven other people, police Captain Abdul Hafez al-Mahlawi said.

Iraqi security forces have been able to hold violence in check, with the number of people killed in the first 11 months of 2012 fewer than in the same period the year before, according to government figures.

"The withdrawal of US forces meant that training became reduced, intelligence gathering became limited and quick reaction forces were no longer as well resourced or able to reach flashpoints at short notice," said John Drake, an analyst with AKE group.

"However, counter-insurgency operations and arrests didn't decline," he said, though "the Iraqi military still has a long way to go in terms of building capabilities, and they remain under-resourced and regularly targeted."