Nine beaches in Sydney’s north have been closed after mysterious balls of debris washed ashore. The marble-sized balls of debris washed up on Tuesday, the Northern Beaches Council said, prompting the closure of nine popular beaches.

Nine beaches have been closed after balls of debris washed ashore, echoing a spate of shorelines to close last year when balls of tar washed up. Northern Beaches Council on Tuesday raised the alarm on the predominantly marble-sized balls of debris.

Nine beaches along Sydney's Northern Beaches have closed for precautionary reasons after numerous tiny balls were found washed up on the shoreline.