The Taliban claimed responsibility for the attack, with spokesman Zabihullah Mujahid saying on Twitter that the blast destroyed the vehicle and killed all on board.
These service members were conducting operations as part of NATO's Resolute Support Mission, the statement added. Qari Yusouf Ahmadi, a spokesman, said it occurred in the southern Kandahar province.
According to the Department of Defense, 2,218 service members have been killed in Afghanistan since 2001, including 26 who died in 2019.
The latest attack seemed certain to stall fresh efforts to restart the peace talks between Washington and the Taliban. 23 US soldiers died in 2019, making it the deadliest year for American service members since the USA amid attempted peace talks with the Taliban. USA special envoy Zalmay Khalilzad is waiting to hear if the Taliban will agree to a temporary ceasefire, which could open the door for the withdrawal of some American troops. He told NPR's Audie Cornish that a diplomatic agreement between the US, the Taliban and the Afghan government is the only way out of the conflict.
Earlier, both North Atlantic Treaty Organisation and Afghan officials had confirmed a roadside bomb hit a USA army vehicle Saturday, without mentioning casualties.
The NATO spokesman said it was assessing the situation but declined to give details.
An Afghan official said the attack had taken place in the Dand district of Kandahar province. The official was not authorized to speak with media and requested anonymity.
The Taliban maintains control over half the country and, even with peace talks in the offing, are carrying out attacks on both American and Afghan government forces almost every day.
While Afghan security forces have also suffered tens of thousands of casualties, civilians continue to bear the brunt of hostilities.
U.S. Ambassador John Bass left Kabul last week, ending his two-year tenure as America's top diplomat.