BAGHDAD: Attacks in Iraq killed 17 people on Thursday, including a family of four murdered with knives, Iraqi officials said, after government figures showed July was the bloodiest month in almost two years.

At least 23 people have been killed in violence in the first two days of August, which have seen a number of attacks on security forces and their facilities, including a prison, a military site and checkpoints.

Militants attacked the house of a Turkmen family in the north oil hub of Kirkuk, cutting the throats of a father, mother and two daughters.

An AFP journalist said the bodies of the husband and wife were in one room, and the two daughters in another. Blood was everywhere.

Neighbours were screaming and crying in the garden of the house. A police source said nothing was stolen, and that it appeared to be a revenge attack.

Gunmen also shot dead four police in Tikrit, north of Baghdad, while three members of the Sahwa anti-Qaeda militia were killed by a bomb near Balad, also north of the capital, security and medical officials said.

In northern Baghdad, a car bomb in the Husseiniyah area killed three people and wounded 11, an interior ministry official said, adding that angry residents then attacked federal police and burned some of their vehicles.

A health ministry official put the toll from that attack at seven killed and 22 wounded.

Gunmen attacked a checkpoint near a police station northeast of Samarra, killing one police officer and one Sahwa member, a police captain and a medical source in Samarra hospital said.

And an army officer said gunmen attacked a checkpoint near Dujail, also north of Baghdad, killing a soldier and kidnapping four others.

In the Euphrates Valley, a police major said a patrol was hit by a roadside bomb in Haditha, wounding four police, while three police were wounded in another attack by gunmen on a checkpoint east of the town.

And south of Kirkuk, six gunmen wearing explosive belts tried to attack a military site but five of them were killed and the sixth seriously wounded and the attack failed, Staff Brigadier General Mohammed Khalaf Saeed al-Dulaimi said.

Al-Qaeda front group the Islamic State of Iraq has said it would look to retake territory, and appealed for Sunni Arab tribes to send fighters, in a recording posted in the name of its leader. Abu Bakr al-Baghdadi.

The message posted on various jihadist forums said the ISI would begin targeting judges and prosecutors, and try to help its prisoners break out of jails.

The latest violence comes a day after official figures put the number of people killed in attacks in July at 325, the highest monthly death toll since August 2010.

While violence has decreased compared to its peak in 2006 and 2007, attacks remain common across Iraq. There were attacks on 27 of the 31 days in July.