Besieged Rio Tinto chief Jean-Sebastien Jacques and two of his top executives face mounting pressure to resign ahead of crisis board meetings which shareholders say loom as "a test" of directors' mettle.

The sharpened calls from investors on Wednesday overshadowed Mr Jacques' first meeting with the Puutu Kunti Kurrama and Pinikura (PKKP) people since Rio detonated explosives on their ancestral land and destroyed prized cultural heritage inside Juukan Gorge.