The three service members' deaths bring the total American deaths in Afghanistan for the month of November to five.
Three US service members have been killed and three others wounded in a bomb explosion near Ghazni city in Afghanistan.
About 15,000 USA troops are deployed to Afghanistan, with most involved in Resolute Support, a US -led North Atlantic Treaty Organisation mission to train, advise and assist Afghan forces battling the Taliban.
Officials would not give further detail until next of kin were notified, saying only that the injured were evacuated and receiving medical treatment.
In a separate incident on Tuesday, the Taliban abducted 21 passengers from two vans that were traveling through the northern Sari Pul province, according to Habibullah Mujahidzada, a district police chief.
He said US Special Forces had been conducting operations with Afghan forces around Ghazni city since Monday. Ghazni was the only province that didn't hold parliamentary elections last month.
There was no immediate claim of responsibility for the attack.
Senior U.S. military officials have sought to reassure Afghan forces.
On Sunday, the DOD had identified the soldier that was killed in the Garmsir District, Helmand Province, Afghanistan from "injuries sustained while engaging enemy forces" the day prior as Sgt. Leandro A.S. Jasso. The great majority of USA forces withdrew by the end of 2014, but those still in the country often are involved in supporting combat situations on the ground as well as by air.
During that same period, 58 US troops were killed, he said.
About 14,000 U.S. troops remain in Afghanistan as part of Resolute Support and a separate counter-terrorism mission aimed against militant groups such as al Qaeda and Islamic State.