A US soldier and at least 16 militants have been killed in an attack on a US and Afghan patrol in southern Zabul province, the US military says.
In a separate incident, two other US soldiers were wounded by a roadside bomb in Ghazni province.
Also in Ghazni province, suspected Taleban militants killed a doctor and a bystander in an attack on a clinic.
Afghanistan has recently seen a rise in violence, amid preparations for September's parliamentary elections.
Speaking after the US soldier's death, Brig Gen James G Champion, said Afghan and US forces would "continue this search and attack mission to ensure there are no enemy safe havens in this region."
In the other incident, four suspected Taleban militants attacked a medical clinic killing a doctor and a bystander in central Afghanistan, officials say.
Police reached the area and arrested two of the militants who were injured in the clash, according to Ghazni province governor Haji Sher Alam.
A man claiming to speak for the Taleban said they carried out Monday's attack in Andar district.
"We killed the doctor, Mohammed Hashim, because he was a former communist and he was also spying for the Americans," said Abdul Latif Hakimi, who says he is a Taleban spokesman.
Mr Hakimi also told the AFP news agency that the doctor was a candidate in the parliamentary elections.
The UN-supported Joint Electoral Management Body and the interior ministry both deny this.
Afghanistan suffers from a severe brain drain and a lack of specialists after decades of unrest.
The country is said to have only one doctor per 50,000 inhabitants.
The US military said in a statement on Tuesday that they had discovered three separate weapons caches in eastern Afghanistan.
One cache, discovered near Nangarhar province, included an anti-aircraft gun and hundreds of anti-aircraft rounds.
The ammunition was destroyed by explosives experts, the statement said.