KABUL, June 4 (Xinhua) -- Two siblings were killed when a piece of unexploded ordnance left over from the past conflicts went off in Afghanistan's eastern Paktia province, a provincial official confirmed on Thursday.

The tragic incident took place in the Spena Takhta area of Rohani Baba district, where the children, both aged 14, discovered the device and were playing with it when it suddenly exploded, killing them instantly, said Mawlawi Nisar Ahmad Nejat, director of the provincial disaster management authority.

In two separate incidents in the neighboring Ghazni province over the past three days, two other children sustained serious injuries from similar unexploded remnants.

Afghanistan remains one of the world's most heavily contaminated countries with landmines and unexploded ordnance, a deadly legacy of more than four decades of successive wars and internal strife. ■