US and Nato forces are battling a rising Taliban insurgency
Nato forces in Afghanistan say that four American service members have been killed in a roadside bomb attack in the west of the country.
Two other roadside bomb attacks on Thursday in Helmand province left five civilians and five policemen dead.
The news comes as new Nato Secretary General Anders Fogh Rasmussen makes his first visit to the country.
In July Nato and US forces suffered their bloodiest month in the eight-year war against the Taliban and al-Qaeda.
A statement from Nato's International Security Assistance Force said on Thursday: "Four Isaf service members died after their vehicle struck an improvised explosive device today in western Afghanistan."
It confirmed the dead were all Americans.
A separate statement confirmed another US soldier was killed by a roadside bomb in western Afghanistan on Wednesday.
Earlier it was reported that another bomb had killed five people travelling to a wedding on a tractor-trailer in the Garmsir district of Helmand province on Wednesday.
Five other people were hurt.
Nato troops are conducting offensives in Helmand ahead of presidential and provincial council elections on 20 August.
Garmsir district is a militant stronghold where US marines have been trying to flush out insurgents ahead of the elections.
The Taliban have ordered a boycott of the elections and have vowed to block roads leading to polling stations. Analysts say violence is mounting as the elections draw nearer.
Five policemen were also killed by a bomb in the Nadali district of Helmand.
The interior ministry said the bomb exploded next to a police vehicle.
The blasts came as Mr Rasmussen visited Afghanistan. He is now in the southern city of Kandahar.
Mr Rasmussen said on Wednesday he was determined to reduce civilian casualties in Afghanistan.
Taliban fighters make roadside bombs, known as IEDs (improvised explosive devices), from mines and explosives.
They are activated by pressure plates, trip wires or mobile phones.