An explosion in eastern Afghanistan killed three NATO soldiers on Monday, the US-led International Security Assistance Force (ISAF) said.
An Afghan police spokesman said the blast was a suicide attack on an ISAF patrol in Khost city and that several civilians had also been killed.
An ISAF spokesman said he could confirm that three NATO service members had been killed, but that details of the incident were still unclear.
The deaths take coalition casualties to at least 347 this year, according to an AFP tally based on the website icasualties.org.
NATO has more than 100,000 troops fighting a Taliban insurgency in Afghanistan, but they are due to pull out by the end of 2014.
The latest blast came a day after NATO announced that a firefight between coalition troops and their Afghan allies killed an ISAF soldier, a civilian contractor and three Afghan army troops in circumstances that remained murky.
The incident was initially described as a suspected insider attack, but it was later suggested that either insurgent fire or a verbal argument between the troops sparked the shooting.