Image caption There are around 140,000 international troops in Afghanistan, mostly from the US

Three soldiers from the Nato-led International Security Assistance Force (Isaf) have been killed in Afghanistan, officials have said.

The three, whose nationalities have not been disclosed in line with policy, died when a roadside bomb exploded in the east of the country.

No further details were immediately available of the incident, which took place on Saturday.

More than 500 Nato troops have been killed so far this year in Afghanistan.

Much of the decade-long Afghan conflict's worst fighting takes place in eastern Afghanistan, close to the border with Pakistan.

Pakistan closed its supply routes to Nato forces in Afghanistan after 24 Pakistani soldiers were killed by a Nato air strike last Saturday close to the mountainous, porous border.