Father sold ancestral property without consent of daughters

We are part of a hindu family. My father has inherited about 10 Acres of agricultural land from his father after his death. My grandfather got this property as a gift and it got transferred onto my fathers name after his death as he is the only son to my grandfather & grandmother. We are 6 siblings (3 sons and 3 daughters) and all married. Our mother died recently and after that my father had sold the property which has transferred onto his name without the consent of daughters. We will have equal share on the property but our father has sold it without our knowledge. Are the property sales made by my father to miscellaneous people legal and valid. Can we (daughters) reclaim the properties sold by him by approaching courts? What are the legal remedies available to us to get back the properties? Do the people who purchased the properties from my father without our consent have any rights over the properties if we approach the courts of law to reclaim our properties? Do we have to pay them back the sale considerations from our pocket or is our father liable to pay? Please advice and guide me in detail. We're literally shattered knowing that he sold off all the properties without leaving us anything.