Four Afghan children were killed Thursday morning when an Improvised Explosive Device (IED) went off in the country\'s southern province of Helmand, a provincial government spokesman said. \"One child touched off an IED early Thursday morning in Safyan area of provincial capital Laghkar Gah. The explosion which took place near a water canal killed four children including two girls on the spot,\" spokesman Omar Zwak told Xinhua. He blamed Taliban militants for bombing in the city, 555 km south of national capital Kabul. Helmand has been notorious for growing poppy and for being the Taliban hotbed. Taliban militants have been largely relying on roadside bombing and suicide attacks in fighting Afghan security force and NATO-led troops based in Afghanistan, often causing civilian casualties. On June 3, up to 10 school children were killed and 15 children were wounded in a suicide bombing in the eastern Paktia province, 100 km south of Kabul. The bombing which hit a military convoy near a school also killed two U.S. soldiers and an Afghan policeman. In an unrelated incident, Taliban ambushed and kidnapped three aid workers of a local None-Governmental Organization (NOG) in the western Herat province, 640 km west of Kabul, on Wednesday evening. \"One woman and two men working for NRC, a local NGO in charges of providing assistance for women, were kidnapped in Snogar area of Guzara district late Wednesday,\" the district administrative chief Nisar Ahmad Popal told Xinhua earlier Thursday. He said the police have conducted a search operation to locate and rescue the victims. The Taliban has stepped up their attacks on Afghan and NATO-led troops since annual rebel offensive was launched in April this year in the war-ravaged country. As many as 2,500 civilians had been killed or injured in Taliban-link insurgency and conflicts from Jan. 1 to mid-June this year, said officials of the United Nations mission in the country.