RAMALLAH, West Bank, March 6 (Reuters) - Two Palestinian children were killed when abandoned ordnance exploded in the occupied West Bank on Tuesday, Palestinian officials said.

Ramadan Awad, police chief in the city of Hebron, said two 12-year-old boys, Hamza and Zayed Jradat, were killed and three teenagers were injured when an old Israeli mortar exploded.

The group had been playing in a field filled with scrap metal in the nearby village of Sier, Awad said.

An Israeli military spokesman said an initial investigation indicated that the blast was caused by "unexploded ordnance that was ignited", but had no further details.

Israeli forces routinely patrol the West Bank, which was captured in a 1967 Middle East War. The Palestinian Authority has had limited self-autonomy there since an interim peace deal in the early 1990s.