Activist investor Elliott Management has quietly built a $1 billion stake in Anglo American (OTCQX:NGLOY), adding pressure to the UK-listed mining giant after it became the target of a $39 billion takeover bid from BHP Group (NYSE:BHP). This development emerged after Anglo American's board rejected BHP's offer, deeming it "highly unattractive" due to its undervaluation of the company's prospects and its complex structure.

According to Bloomberg, Elliott Management, led by billionaire Paul Singer, has amassed this holding over the last months. Persons with knowledge of the matter requested anonymity due to the confidential nature of the...