SYDNEY - Baffled Australian police launched an appeal for information on Tuesday after a 700-year-old skull washed up on a beach.

Police believe the skull must belong to a private collector or museum, but are mystified as to how it arrived on the Sydney beach in September.

"Detectives are now looking for the owner of the skull, who they believe may be a private collector or from a museum or research facility," they said.

Tests showed the skull belonged to a non-Aboriginal child aged between four and six who lived about seven centuries ago.

Police said any claim for the skull would require records or some other proof of ownership.