Two NATO service members were killed on Monday in separate incidents in restive southern Afghanistan, the military alliance said on Tuesday. \"An International Security Assistance Force (ISAF) service member died following an insurgent attack in southern Afghanistan yesterday,\" the NATO-led ISAF said in a statement. The second service man lost his live in an Improvised Explosive Device (IED) attack also in the southern part of the country, which is known as Taliban insurgents\' stronghold. The ISAF generally does not disclose the identity of the casualties, saying \"It is ISAF policy to defer casualty identification procedures to the relevant national authorities.\" Troops mainly from the U.S., Britain, Canada and Australia have been stationed in the southern region within the framework of the ISAF to fight Taliban militants there. The Taliban stepped up their attacks on Afghan and NATO-led troops since a spring rebel offensive was launched in May this year in the war-ravaged country. Over 530 NATO soldiers, most of them Americans, have been killed in Afghanistan since the beginning of this year.