Australian Military sources say that the blast ripped through the foreign troops' convoy north of Helmand Province on Saturday, Press TV reported.
The attack comes after Taliban militants announced on Thursday that they will launch their annual "spring offensive" across Afghanistan, vowing to increase their attacks on the US-led forces in the country.
According to official figures released by the website, icasualties.org, 143 foreign soldiers have lost their lives in war-battered Afghanistan so far this year.
The increasing number of military casualties in Afghanistan has caused widespread anger in the US and other NATO member states, undermining public support for the Afghan war.
The US-led invasion of Afghanistan took place in 2001. The offensive removed the Taliban from power, but insecurity continues to rise across Afghanistan despite the presence of thousands of US-led troops there.