The investor group led by Saba Capital Management founder Boaz Weinstein looking to acquire Sculptor Capital Management, has again upped its offer for the hedge fund firm, prompting Rithm Capital Corp to consider improving its offer, according to a report by Bloomberg.

The report cites unnamed sources familiar with the matter as confirming that Weinstein's consortium of investors, which includes billionaires Bill Ackman, Marc Lasry and Jeff Yass, approached Sculptor over a week ago with an improved $13-a -share offer, up form an earlier bid of $12.76.

Shares in the firm jumped 5.4% to $12 in extended trading at 5:58 pm in New York on Monday, after Bloomberg first reported the revised offer.

Rithm has reportedly now held talks with Sculptor about increasing its offer of $11.15 a share, or $639 million, according to Bloomberg's sources