A NATO soldier was killed in an explosion in Afghanistan's restive southern region on Tuesday, bringing the number of the military alliance casualties to two since Monday morning, NATO said in a statement.

"An International Security Assistance Force service member died following an improvised explosive device (IED) attack in southern Afghanistan today," said the statement issued by NATO-led International Security Assistance Force (ISAF) here on Tuesday.

However, the brief statement did not disclose the victim's casualties, only saying "it is ISAF policy to defer casualty identification procedures to the relevant national authorities."

Troops mainly from U.S., Britain, Canada and Australia have been stationed in the southern region within the framework of ISAF to fight Taliban militants there.

Another NATO soldier was killed in similar incident in southern Afghanistan on Monday.

The simple but difficult to be detected Taliban weapon, the Improvised Explosive Device (IED), used in making suicide vests and roadside bombs, has proved a challenge for Afghan and NATO-led forces in the insurgency-hit country.

Over 400 NATO soldiers, most of them Americans, have been killed in Afghanistan since the beginning of this year.