Zambia's President Edgar Lungu has said some church officials and traditional leaders are to blame for a recent spate of mob attacks that have left at least 50 people dead.

The lynchings have targeted people accused of involvement in a series of mysterious assaults with chemical spray that have harmed well over 1,000 Zambians since December and caused public panic.

The spray has left children and adults unconscious; there's speculation the assailants seek to use the victims' blood for witchcraft.

The attacks were initially confined to the mineral-rich Copperbelt province but have since spread to the capital Lusaka.

Hundreds have been arrested in connection with the vigilante revenge attacks.