KABUL - Four Nato soldiers have been killed in bomb blasts in southern Afghanistan, the International Security Assistance Force said Sunday. The soldiers died "following separate improvised explosive device attacks" on Saturday, ISAF said in a statement, without providing further details or the nationalities of the victims.The latest deaths take the toll among Nato troops in Afghanistan this year to 169 and the total in 10 years of war to 3,016, according to an AFP count based on records kept by icasualties.org. Nato has some 130,000 troops in Afghanistan but they will withdraw by the end of 2014, leaving the fight against Taliban insurgents to Afghan forces. The Taliban have stepped up their attacks across the country since announcing the start of their spring offensive at the beginning of May.