Two Afghan policemen were killed and three injured when the warplane of NATO-led forces mistakenly targeted a police checkpoint in eastern Ghazni province, police said on Saturday. \"Two policemen with Afghan National Police (ANP) were killed and three others injured when their checkpoint was attacked erroneously by international forces\' plane at about 00:30 local time Saturday,\" provincial police chief, Zarawar Zahid told Xinhua Saturday morning. Zahid said an investigation was launched to probe the incident in the province 125 km south of capital city of Kabul. In an unrelated incident, two militants were killed Saturday morning when their bomb went off prematurely in country\'s eastern Nangarhar province. \"Two militants were busy in planting a roadside bomb along a road in Pachir Wa Agam district but their explosive went off prematurely at around 04:00 a.m. (local time) Satruday killing them on the spot,\" administrative chief of Pachir Wa Agam district of Nangarhar province, Azizullah Shinwari told Xinhua. The Taliban-led insurgency has been rampant since the militant group announced to launch spring offensive from May 1 against Afghan and and over 130,000 NATO-led troops stationed in Afghanistan. Taliban militants as part of tactic have resorted to suicide attacks and roadside bombings which often claim civilians. Four civilians were killed as a motorbike bomb went off in Uruzgan province 370 km south of Kabul on Thursday night, according to provincial officials.