KANDAHAR, Afghanistan -- During the long Afghan winter, Taliban insurgents were apparently busy underground.

The militants say they spent more than five months building a 1,050-foot tunnel to the main prison in southern Afghanistan, bypassing government checkpoints, watch towers and concrete barriers topped with razor wire.

The diggers finally poked through Sunday and spent 4 1/2 hours ferrying away more than 480 inmates without a shot being fired, according to the Taliban and Afghan officials. Most of the prisoners were Taliban militants.

Accounts of the extraordinary prison break, carried out in the dead of night, suggest collusion with prison guards, officials or both.

Following a recent wave of assassinations here, the breakout underscores the weakness of the Afghan government in the south despite an influx of international troops, funding and advisers. It also highlights the spirit and resourcefulness of the Taliban despite months of battlefield setbacks.

Officials at Sarposa prison in Kandahar city, the one-time Taliban capital, say they discovered the breach about 4 a.m. Monday.