Kabul  - An airstrike by US-led coalition forces mistakenly killed four Afghan police in southern Afghanistan, while a district governor, a tribal chief and two US soldiers were killed in roadside blasts in the same region, officials said Wednesday.

Taliban militants attacked a police post in the Qale Qazi area of Ghazni, the provincial capital of the province of the same name, early Wednesday, Ismail Jahangir, spokesman for the provincial governor said.

The US-led coalition forces conducted an airstrike in the area, killing "several Taliban," he said, adding, "Unfortunately the airstrike also killed four of our police forces and wounded two others."

Jahangir said the provincial authorities along with US military officials have started an investigation.

Meanwhile, a district governor for Reg in southern Kandahar province was killed when the vehicle he was driving in was blown up by a roadside bomb, Gholam Ali Wahdat, a police commander in the region, said.

Wahdat said one other person driving in the same car was killed and a third person was wounded in the blast, for which he held Taliban militants responsible.

Two NATO-led soldiers were killed in a similar bomb blast in the same southern region on Tuesday, the alliance said in a statement on Wednesday.

The statement quoted a US press officer, Captain Regina Gillis, as confirming that the deceased were US service members.

Taliban attacks have been increased as around 17 million registered voters are expected to come out on Thursday and elect a president and 420 provincial council members for the country's 34 provinces.

The militants also fired two rockets into the northern city of Kunduz on Wednesday afternoon, causing no damage or casualties, Mahboobullah Sayedi, spokesman for the provincial governor, said.

The militant group vowed to disrupt the vote and has warned it will slit the throats and chop off fingers of anyone who voted on Thursday.

But Afghan and NATO military officials assured that their 300,000 troops were on high alert and were prepared to neutralize any attack that is mounted by Taliban militants.(dpa)