NATO's International Security Assistance Force (ISAF) will end its combat mission later this year, leaving the Afghan police and army to take on full responsibility for battling the resilient Taliban insurgency.
"Three ISAF service members and one ISAF canine died following an improvised explosive device attack in southern Afghanistan today," the NATO force said in a statement.
Military dogs are often used to sniff for explosives, though they have proved unpopular with Afghan civilians as they are seen as unclean by many Muslims.
The attack occurred in the volatile Nad Ali district of Helmand province, according to Afghan officials.
"The bomb was carried on a motorbike and detonated close to an ISAF patrol," the provincial governor's spokesman Omar Zawak told AFP.
The Taliban claimed responsibility via a text message sent to the media.
The last major incident involving NATO troops was ten days ago when five US soldiers were killed in an accidental "friendly fire" air strike in Zabul province during clashes with insurgents.
