KABUL (AFP) Two Nato soldiers were killed by an improvised bomb in northern Afghanistan Wednesday, as the foreign alliance continued to suffer a surge of attacks in the war-torn country. The soldiers, whose nationalities were not released, were part of Natos International Security Assistance Force, whose estimated 142,000 troops in Afghanistan are set to increase to 150,000 by August. Last week Nato forces suffered their bloodiest spate of the year as 30 soldiers were killed, including four Americans when the Taliban shot down a helicopter in southern Helmand province. Violence, mainly linked to a Taliban-led insurgency, has claimed the lives of 266 Nato soldiers since the start of the year, according to an AFP tally based on the independent icasualties.org website.