Afghan troops clashed with drug smugglers near a government post in a remote area of Kandahar province on Saturday, said Mohammad Anas, deputy governor of the province.
The fighting left five soldiers dead and three wounded, Anas added.
The soldiers were killed after they tried to stop the smugglers from trafficking drugs into Pakistan, a key export source for Afghan narcotics.
In another incident on Saturday, four Taliban members were killed in a clash with troops in Helmand province while they were planting land mines on a road often used by soldiers, a spokesman for the provincial governor said.
Violence, including twin bomb blasts on Tuesday in Kandahar, has killed 51 people and wounded several dozen in less than a week in southern Afghanistan, underlining growing insecurity.
More than 450 people including 'militants', Afghan troops, civilians, aid workers and more than 12 members of US-led troops have been killed since August in violence largely blamed on the Taliban.
President Hamid Karzai vowed on Saturday the violence would not deter him from rebuilding Afghanistan, battered by 23 years of invasion and civil strife.
Doubts over elections
The deadly attacks in the past week has cast fresh doubts over Afghanistan's plan to hold its first ever free elections in June.
President Karzai has vowed to
hold polls by June
Analysts say Karzai is under pressure from his backers in Washington to hold the vote as soon as possible, so it can be touted as a foreign policy victory by President George Bush, as he seeks re-election in November.
But the consequences could be seriously damaging for Afghanistan, they warn.
"It is far too soon," said Ahmad Rashid, an Afghan expert based in Pakistan. "I think they should be postponed for at least a year, perhaps until spring 2005."
Karzai vowed on Saturday to contest the presidential election and reiterated he aimed to hold it as planned in June.
However, UN officials have said June looks an impossible target, unless security improves significantly.
UN Secretary-General Kofi Annan warned Afghanistan faced "a deterioration in security at precisely the point where the peace process demands the opposite".