Roadside bombs killed five Nato service members in southern Afghanistan on Friday, the alliance said.
Nato did not identify the troops or disclose what countries they came from.
The deaths brought to nine the number of coalition troops killed in the first week of the year. At least 544 Nato troops died in Afghanistan in 2011, the second-deadliest year for the coalition in the decade-old war.
Four troops died in one of Friday's bombings, and one was killed in a separate blast. The alliance said both incidents occurred in southern Afghanistan.
Nato is gradually handing over responsibility for security to the rapidly expanding Afghan police and army. Coalition forces plan to cease combat operations in 2014, when most foreign troops will be withdrawn.