Three policemen were killed in a pre-dawn raid on Sunday by suspected Taliban fighters in the southeastern province of Khost near the border with Pakistan.
Hours later, two civilians were killed by a roadside bomb that was apparently aimed at a vehicle carrying members of a western security firm near the city of Heart.
The sixth victim was Mohammad Yunus Hosseini, a provincial delegate, who was shot outside his office in the southern city of Kandahar by a man riding a motorbike.
The attacks came as authorities searched for Gabriele Torsello, a Italian photojournalist who is believed to have been kidnapped.
The Taliban have denied any role in the abduction which comes just over a week after two German journalists were shot dead in the relatively safer north of Afghanistan.
A spokesman at the UN mission in Afghanistan said police were investigating and the UN was monitoring the situation.
"We hope that the authorities will leave no stone unturned in trying to investigate this matter and ensure the safe return of this photojournalist," spokesman Aleem Siddique told reporters.
Although Afghan authorities have yet to confirm Torsello has been kidnapped, Italy's foreign ministry said on Sunday it believed he had been abducted.
More than 2,500 people have been killed in Taliban-led violence and foreign troops operations this year in Afghanistan.
The death toll includes hundreds of civilians, aid workers, Afghan forces and over 140 foreign soldiers.