A US soldier has been found guilty by a court martial in Kabul of assaulting prisoners in an American military base in Afghanistan's Uruzgan province.
Rights groups have made a number of abuse allegations
Sgt Kevin D Myricks was found guilty of one count of conspiracy to maltreat and two counts of maltreatment, a US military statement said.
Myricks has been reduced in rank and sentenced to six months' detention.
On Saturday, another soldier, James Hayes, was sent to four months in prison for the same incident of abuse.
Human rights groups have often accused US forces of abusing Afghans held at detention centres in the country.
The US military says the detainees did not require medical attention as a result of the assault last July.
Myricks has been demoted to the rank of a private and he is being held in custody at Bagram airfield, the US led-coalition's headquarters in Afghanistan.
He will be transferred to Kuwait soon to serve his six-month sentence.
"The court martial and subsequent punishment in this case reflects the seriousness with which this command views this incident," Maj Gen Jason Kamiya, the coalition's operational commander, said in a statement.
"Incidents of this nature are not reflective of the standards adhered to by this command. We are fully committed to investigating all allegations... and will hold accountable those who are found to have acted inappropriately."
Myricks was assigned to Company C, 96th Engineer Battalion, when the incident took place last July.
A third soldier is also facing "non-judicial punishment for allegedly having knowledge of the abuse and not reporting it through the unit's chain of command", the US military has said.
The charges against the soldiers came in October, close on the heels of accusations that US forces had burned the bodies of Taleban fighters, an act considered sacrilege in Islam.
At least eight prisoners have died in US custody since 2001.
In September, a US military interrogator was sentenced to five months in prison for assaulting a detainee in Afghanistan who later died.
Five other US soldiers have been convicted following the deaths of two prisoners at the military base at Bagram, outside Kabul, in 2002.