In the suicide attack, Nato soldiers were helping to build a bridge in eastern Afghanistan when the bomber struck, killing three and wounding six, Nato said.
Afghan security officials also reported six Afghan soldiers and more than 20 Taliban fighters killed in separate incidents across the country.
More than 3,900 people, mostly fighters, have died this year, according to an Associated Press tally of casualty figures provided by Western and Afghan officials.
In the eastern province of Nangarhar, a roadside bomb hit a vehicle carrying Afghan National Army troops on Monday, killing four, the defence ministry said.
On Monday, Nato and Afghan soldiers killed 15 armed fighters near the Taliban stronghold of Musa Qala in the southern province of Helmand, officials said.
Afghan forces backed by US-led multinational force soldiers also foiled an attempted Taliban ambush in Kandahar, killing seven fighters, the military said.
Foreign soldiers in Afghanistan have been hit by a wave of attacks that have left 153 dead since January.