The attacks came the same day as the head of US-led coalition forces in Afghanistan warned that the Taliban were stepping up plans to disrupt the presidential elections on 9 October.
Hajji Muhammad Wali, spokesman for the governor of Helmand province, said an unspecified number of armed men launched raids on three security posts along a road between Girishk in the southern Helmand province and Delawar in the western province of Farah.
Three soldiers were killed in the first attack, six in the second and there were no casualties in the third.
Wali blamed the "enemies of Afghanistan", who he says oppose the upcoming elections.
A Taliban spokesman said fighters had carried out the attacks and that 15 government soldiers had been killed and two captured.
In Kabul, the US military's commander in Afghanistan said US-led coalition forces had intelligence reports saying Taliban fighters were stepping up plans to disrupt the election.
Interim President Hamid Karzai
(L) is a US favourite for elections
"For all terrorists in the region ... disrupting the election is part of their agenda," Lieutenant General David Barno told a news conference in Kabul.
More than 17,000 US and allied troops are fighting an insurgency waged by the Taliban.
Taliban fighters were also allegedly linked to a rocket attack on the helicopter of US-approved interim President Hamid Karzai - a US-supported favourite to beat 17 opponents at the polls - as he made a rare visit outside Kabul earlier this month.
Karzai was also described as untrustworthy by local leaders, who added that he was using the state for campaigning purposes.
"Our challenge ... is to rise up to the level of resolve shown daily here by our hosts, the people of Afghanistan"
Lieutenant General David Barno,
Commander of US-led forces in Afghanistan
Other Afghan leaders, such as Qulb al-Din Hikmatyar, have accused the Bush administration of exploiting Afghanistan, especially with regard to the upcoming election in order for it to seem as if Bush has at least one success story compared to Iraq.
Desire for peace
Barno said the insurgency was being waged by a "tiny minority", and that the rest of the world owed it to Afghanistan to stand by them.
"Our challenge ... is to rise up to the level of resolve shown daily here by our hosts, the people of Afghanistan," he said. "We must remain resolute, we must stay the course."
Barno said the fact that more than 10 million Afghans had registered to vote - more than 40% of them women - showed the country had a real desire for peace and democracy.
But Aljazeera.net was told by residents that they were at times being coerced into getting registered.
Residents have added that they are being harassed in the evening by one group who say they should not support the US and its ally, Karzai, while in the morning government officials threaten people by saying that they will be deprived of basic amenities such as medical care, food aid, water and security if they do not.
Some voters say they are being
coerced to get a 'Karzai card'
This, they say, is the reason for the high number of people holding a "Karzai card" (voter card), residents say.
They also told Aljazeera.net that while politicians lived a luxurious life, the people were suffering and the world seemed to have lost interest.