The rejection of Citigroup's offer follows that of Orbis Investment Management, which earlier this week put its shares on the market at 1,900 yen each.
It is thought that the two funds, which between them own a stake of ten per cent in the scandal-hit Japanese brokerage, perceive they can force Citigroup to up their offer.
Commenting on the developments, Ken Masuda of Shinko Securites told Reuters: "They are trying to send a message - 'If you want Nikko so much, why don't you pay this level?'"
Citigroup has been eyeing a takeover of its partner Nikko to limit the damage to its reputation after the brokerage was embroiled in an accounting scandal last year that led to the resignation of several top-level staff.
Japanese bank Mizuho has offered all its shares in Nikko to Citigroup, which if acquired would bring the US banking giant's stake in Nikko to around ten per cent.