Fortress Investment Group, the listed private equity and hedge fund group, has ­suspended redemptions at its flagship Drawbridge Global Macro Fund after investors sought to withdraw more than $3.5bn in funds, ­according to a regulatory ­filing on Wednesday.

Fortress took the action, at least in part, because the fund – which had $8bn under management as recently as September – has to keep a minimum level of assets or risk having to unwind ­derivatives trades, a person familiar with the matter said.