Six soldiers of the NATO-led International Security Assistance Force in Afghanistan (ISAF) were killed in southern Afghanistan, NATO said Friday. Three of the soldiers died in a firefight with Taliban insurgents in the context of Operation Mushtarak in Helmand province Thursday night, a NATO press release reported. Three others were killed by an explosive device, also late Thursday, according to dpa. Operation Mushtarak, which means "together" in Dari, entered its sixth day Friday, as over 15,000 soldiers pushed through Helmand province in an effort to displace the Taliban.