BAGHDAD — A series of attacks across Iraq on Sunday killed 15 people, including a random shooting and the killing of a judge, authorities said.

Violence has been on the rise in Iraq all year, but the number of attacks against civilians and security forces has spiked during the Islamic holy month of Ramadan, which began early last month. The surge in the bloodshed is raising fears of a return to the widespread killing that pushed the country to the brink of civil war after the 2003 U.S.-led invasion.

The deadliest attack took place late Sunday night when gunmen in a speeding car opened fire randomly on a gathering of people on a street in the oil-rich city of Kirkuk, killing four people and wounding three, said Kirkuk deputy police chief Maj. Gen. Torhan Abdul-Rahman Youssef.

A bomb later exploded inside a cafe in western Baghdad shortly before midnight, killing three and wounding 12, police said.

Earlier in the day, police officials said a roadside bomb struck an army patrol near the northern city of Mosul, killing three soldiers.

In Tikrit in central Iraq, a car bomb killed Judge Sajid Abdul-Amir as he was driving to his work, police said.

In eastern Baghdad, two people were killed in a blast, police said. Meanwhile, mortar rounds landed on houses in the capital's western suburbs, killing two people, authorities said.

Medical officials confirmed the casualty figures toll for the attacks. All officials spoke on condition of anonymity as they were not authorized to talk to the media.

There was no immediate claim of responsibility for the attacks, though security forces and civilians are frequently targeted by al-Qaida's Iraq branch.

With Saturday's attacks, at least 612 people have been killed since the start of Ramadan, according to an Associated Press count. Along with security officials being killed, there have been multiple bloody attacks targeting civilians in cafes as they broke their daily fast. It's been the bloodiest Ramadan in Iraq since 2007.

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  • An Iraqi man inspects a burnt-out vehicle at the site of a car bomb explosion in the Hurriyah area of eastern Baghdad, on July 3, 2013 following several attacks the previous day. (AHMAD AL-RUBAYE/AFP/Getty Images)

  • An Iraqi policeman inspects the damage outside a supermarket in central Baghdad's commercial Karrada neighbourhood on June 25, 2013 after a car bomb exploded in the parking area the night before. (ALI AL-SAADI/AFP/Getty Images)

  • A man looks at a destroyed shop following a car bomb in the Shuala area of eastern Baghdad, on July 3, 2013, following several attacks the previous day. (AHMAD AL-RUBAYE/AFP/Getty Images)

  • People and security forces inspect the scene of a car bomb attack in Basra, 340 miles (550 kilometers) southeast of Baghdad, Iraq, Tuesday, July 2, 2013. (AP Photo/ Nabil al-Jurani)

  • Iraqis inspect the aftermath of a car bomb attack at Baghdad's mostly Shiite neighborhood of Husseiniyah, Iraq, Tuesday, June 25, 2013. AP Photo/ Khalid Mohammed)

  • Iraqi men look at the aftermath of a car bomb attack on July 3, 2013 following an explosion the previous day at a convenience store in the northern Baghdad neighbourhood of Shaab. (ALI AL-SAADI/AFP/Getty Images)

  • An Iraqi policeman checks his weapon at a checkpoint in Baghdad on July 1, 2013. (SABAH ARAR/AFP/Getty Images)

  • Iraqis inspect the damage outside shops in Baghdad on June 25, 2013 following an explosion the night before. (SABAH ARAR/AFP/Getty Images)

  • Civilians inspect a crater caused by a car bomb attack in the east Baghdad neighborhood of Kamaliya, Iraq, Wednesday, July 3, 2013. (AP Photo/ Karim kadim)

  • Civilians seen through a broken window of a destroyed car inspect the aftermath of a car bomb attack in the east Baghdad neighborhood of Kamaliya, Iraq, Wednesday, July 3, 2013. (AP Photo/ Karim kadim)