Bill Gross, the co-chief investment officer at bond giant Pimco, lambasted billionaire investor Carl Icahn on Thursday for his involvement in Apple's strategy.

Gross said on Twitter: "Icahn should leave #Apple alone & spend more time like Bill Gates. If #Icahn's so smart, use it to help people not yourself."

Icahn implored Apple to commence an immediate tender offer of $150 billion in a public letter to Apple CEO Tim Cook on Thursday.

The letter, issued in conjunction with Icahn's new website "Shareholders Square Table," comes after Icahn urged Cook this summer to use Apple's $150 billion in surplus cash to buy back company shares.

(Reporting by Jennifer Ablan; Editing by James Dalgleish)