A criminal court judge was among three people killed in gun and bomb attacks north of the Iraqi capital on Sunday, security and medical officials said, in the latest in a spike in nationwide unrest.

In the restive city of Mosul, gunmen shot dead Judge Abdul Latif Mohammed while he was driving home, said police First Lieutenant Mohammed al-Juburi and Dr Mahmud Haddad in Mosul's main hospital.

Three roadside bombs near two schools in Tikrit, 160 kilometres (100 miles) from Baghdad, detonated as middle-school students took their end-of-year exams, killing a policeman and wounding two colleagues, police and a doctor said.

Both spoke on condition of anonymity.

And in the central province of Diyala, gunmen opened fire on an army checkpoint in Khan Beni Saad, a town just north of Baghdad, killing First Lieutenant Omar Ahmed and wounding two other soldiers, the sources said.

The violence comes amid a spike in attacks in Iraq, with the country suffering a wave of attacks in June that left at least 282 people dead according to an AFP tally, though government figures said 131 Iraqis died.

While violence in Iraq has declined dramatically since its peak in 2006-2007, attacks remain common across the country.