Four US soldiers were killed in an explosion in southern Afghanistan on Monday

Four US soldiers were killed in an explosion in southern Afghanistan on Monday, reports say.

The incidence was caused by the eplosion of a homemade bomb known as Improvised Explosive Devices or IEDs.

IEDs are widely used by insurgets to target Afghan and foreign forces in different parts of the country.

The bulk of Western casualties in Afghanistan are caused by IED attacks.

The surge in violence that has accompanied the start of the spring "fighting season" has taken a heavy toll on civilians in recent days as well, particularly children.

Officials in Kunar province, in eastern Afghanistan, have said Monday that at least three civilians were killed and eight injured in an apparently misdirected mortar attack by insurgents against a remote American base.

The Nato has condemned the attack whose victims reportedly included women and at least one child.

Violence is increasing as Afghanistan is approaching the first phase of security transition scheduled to begin in July this year.

US Defence Chief Robert Gate recently told CBS that it was premature to start a speedy withdrawal of troops from Afghanistan.