French reinsurer Scor SA today offered to buy Swiss rival Converium Holding AG in a hostile bid valuing its Swiss rival at 3.1 billion Swiss francs ($2.5 billion).

Paris-based Scor, which already owns 32.9 percent of Converium's stock, will offer 4 francs ($3.25) in cash and 0.5 new Scor shares for each Converium share, chief executive officer Denis Kessler said today. The Swiss company previously rebuffed the approach.