Armed men forced Abdul Hadi out of his house in Hazarjoft, a district in the restive southern province of Helmand, and gunned him down late on Thursday, provincial spokesman Mohammed Wali said on Friday.
"It is the work of the enemies of Afghanistan," Wali said.
Afghan officials frequently use this term to refer to fighters from the Taliban government, which was ousted by US-led forces and Afghan militias in late 2001.
The killing came a day before the Taliban called on Afghanistan's 12.5 million voters to boycott Sunday's elections, which they called an American plot.
They also warned Afghans they could be hurt in attacks on foreign troops if they vote.
US soldiers hurt
Also on Friday, the US military disclosed that a roadside bomb had killed an Afghan interpreter and wounded two US soldiers during a security patrol for this weekend's milestone parliamentary polls.
The blast hit their vehicle late on Thursday in the central province of Ghazni as "the unit was conducting a combat patrol in order to disrupt enemy operations aimed at affecting the elections", it said in a statement.
About 20,000 US soldiers are in
Afghanistan battling insurgents
"Both service members were medically evacuated to Kandahar airfield and are in stable condition," the statement said.
The Taliban previously said they would not target polling stations, but their spokesman Abdul Latif Hakimi said that if Afghans were to vote they would do so at their own risk.
He said the fighters would target foreign "occupation" troops on election day, and these attacks could hurt ordinary Afghans.
"The Taliban shura council appeals to the Afghan people not to take part in the September 18 elections as this election farce is also an American plan," he said, referring to the insurgents' council of clerics.
"Therefore, not only should the Afghan people stay away from the elections, they should also try to sabotage them," he said.
Ban on rallies
On Friday authorities banned campaign rallies, TV adverts and all other forms of electioneering in the final 48 hours before the vote on Sunday, which sees 5800 candidates vying for almost 250 seats in parliament.
More than 12 million Afghans are eligible to vote in the elections, the next phase in international efforts to bring democracy to Afghanistan following years of Soviet occupation, civil war and Taliban rule.
"The Taliban will try to ensure that only foreign troops are targeted and that the Afghan people remain safe"
Abdul Latif Hakimi,
Bronwyn Curran, spokeswoman for the joint UN-Afghan election management team, said campaigning had ended early so voters will not be distracted.
"The reason for the silence period is to allow voters to very carefully consider their choices without being distracted by campaigning," Curran said.
US President George Bush telephoned his Afghan counterpart Hamid Karzai on Thursday to say he was "delighted" with the preparations for the polls, which are being funded by the international community.
In the capital Kabul, almost every available billboard, lamp-post and wall has been plastered with brightly coloured campaign posters.
The elections are being held on a non-party basis, meaning there are many more people competing for seats than would be the case in a two- or three-party system.
During the nearly month-long campaign period that began on 17 August, candidates including tribal commanders as well as former and current Taliban loyalists have been trying to rally support.
Female candidates have also been campaigning, a new phenomenon in the conservative Islamic country, where less than four years ago the Taliban virtually banished women from public life.
Female candidates were a novel
feature of the poll campaign
But Human Rights Watch on Thursday said the elections were taking place in a "climate of fear" after a series of attacks and criticised what it said were rights abusers among the candidates.
The Taliban, who were ousted in a 2001 military operation involving US-led warplanes and Afghan commanders, have ratcheted up the violence in southern and eastern Afghanistan in the run-up to the polls.
On Wednesday US forces backed by warplanes and helicopter gunships killed four suspected fighters after another roadside bomb wounded an American soldier in southern Afghanistan, another US statement said.
A joint Afghan-US patrol was hit by the improvised bomb and then by small arms fire and rocket-propelled grenades in Tarin Kowt, a district in the troubled province of Uruzgan, the statement said.
"The ensuing firefight left four enemy confirmed dead," the statement said, adding that US forces pursued the attackers and arrested five suspects in a nearby village.
Some 12.5 million Afghans will
cast their votes on Sunday
More than 1000 people have died since the start of the year. Most were fighters killed in US air strikes and attacks but 50 American soldiers have also been killed by hostile fire.
Election candidates have also been targeted, with at least six dying in attacks. Most were blamed on the Taliban or other Muslim fighters.
The Afghan government said on Thursday it was deploying 100,000 troops and police for the polls.
There are also around 20,000 US troops and 11,000 Nato-led peacekeeping soldiers helping to maintain security.