* Move makes Cerberus Commerzbank's 2nd-biggest shareholder
* Other major shareholders are the German govt, BlackRock (Updates with approximate value of stake, shareholder ranking)
FRANKFURT, July 26 (Reuters) - Commerzbank said on Wednesday that U.S. buyout fund Cerberus has amassed a stake controlling 5.01 percent of the German bank's voting rights, as of July 25.
Cerberus now ranks as Commerzbank's second-largest shareholder, behind the German government with a 15.6 percent stake and marginally ahead of BlackRock with a 5.0 percent stake, according to Thomson Reuters data.
The value of the stake is about 678 million euros ($789.1 million), based on current market capitalization.
Shares in Commerzbank extended gains on the news, trading 1.4 percent higher by 1308 GMT, putting them among the top gainers on Germany's blue-chip DAX index, which up 0.4 percent.
A spokeswoman for Commerzbank declined to comment. Representatives for Cerberus did not immediately respond to phone calls or emails sent to their New York offices.
($1 = 0.8592 euros) (Reporting by Tom Sims and Alexander Huebner; Editing by Maria Sheahan)