A lava-spewing fissure has opened up along Iceland's Sundhnúkur crater row as the Reykjanes peninsula experiences another volcanic eruption.

A volcano erupted on Wednesday in southwest Iceland, authorities said, with live media images showing it belched smoke and dramatic flows of glowing hot yellow and orange lava, the latest in a series of outbreaks near the capital in recent years.

An official said the eruption near Reykjavik, the 12th in four years from the same volcanic system, posed no threat to people or infrastructure.