* B. Braun wins blocking minority with 11 pct stake
* Was opposed to takeover by Fresenius
* Rhoen agreed to sell most hospitals to Fresenius
* B. Braun says wants two supervisory board seats at Rhoen (Adds comments by B. Braun, Fresenius)
FRANKFURT, Oct 15 (Reuters) - German medical supplies maker B. Braun has taken a minority blocking stake in Rhoen-Klinikum , it was announced on Tuesday, complicating a battle for control of the hospitals chain which wants to sell most of its assets to rival Fresenius for nearly 3.1 billion euros ($4.1 billion).
B. Braun has raised its stake in Rhoen-Klinikum to 11 percent from a previous holding of 5 percent.
This gives B. Braun the right to veto major strategic decisions such as a takeover of the group because Rhoen's bylaws require an unusually high approval rate of more than 90 percent of the shareholder capital for such moves.
Braun is concerned that it would lose Rhoen as a major customer were Fresenius and Rhoen to merge, while unlisted hospitals chain Asklepios, owner of a 5.01 percent stake in Rhoen, has also sought to block a deal, fearing the emergence of a dominant rival.
Fresenius competes with B. Braun, owned by the family of Chairman Ludwig Georg Braun, in supplying medical equipment to hospitals.
In a statement on Tuesday, Rhoen-Klinikum said it was informed that B. Braun intends to further increase its stake in the company within the next 12 months.
Last week B. Braun won antitrust approval for raising its stake in Rhoen to 25 percent, the country's Federal Cartel Office said.
B. Braun also said in a statement on Tuesday it had filed a request with a court to have two representatives on Rhoen's supervisory board, seeking to fill the seats that were vacated by the resignation of two board members last month.
"B. Braun continues to pursue the strategic goal of securing the long-term position of minority shareholdings," the company said.
Rhoen's chairman and founder Eugen Muench, who last year failed to overcome opposition from B. Braun and Asklepios to an outright sale to Fresenius, instead hammered out a deal in September to sell hospitals accounting for about two thirds of Rhoen's revenues to Fresenius for 3.07 billion euros.
Muench and Fresenius have said that unlike a full takeover the sale by Rhoen of most of its hospitals to Fresenius does not require a shareholder vote at Rhoen.