THE HAGUE, Netherlands (AP) — A Dutch father accused of holding six of his children against their will on an isolated farm for nine years is now also suspected of sexually abusing two of his other children, prosecutors said Thursday.

The abuse allegations add a grim new element to a case that is shrouded in mystery and garnered huge attention across the Netherlands.

The 67-year-old father and a 58-year-old man, who is reportedly an Austrian national and rented the farm to the family, are suspected of illegal deprivation of liberty and abuse for their alleged detention of six young adults on a...