North Korea slammed a display of Christmas lights staged by a South Korean church group near the tense border as an "unacceptable provocation".
The giant display -- featuring thousands of glittering bulbs on a tree-shaped steel tower -- was put up Saturday on a military-controlled hill at Gimpo, west of Seoul.
The lights, which can be seen several kilometres away in the impoverished North which suffers chronic power shortages, will remain switched on until early January.
The North's official Korean Central News Agency said the display is an undisguised challenge to us and an unacceptable provocation.
It warned that staging "psychological warfare" along the border would be a "rash act" that could ignite war on the peninsula.