Berlin, April 18 (QNA) - One man was killed, and four others seriously injured in a powerful explosion inside a pedestrian tunnel in Volklingen, western Germany.

German police said the injured include two men in life-threatening condition.

Investigators believe the blast was caused by human action, without providing further details.

A security cordon has been imposed around the site as authorities continue efforts to determine the cause.

Volklingen, with a population of around 40,000, lies near the French border. (QNA)