Hanover-based Continental said that the German ball-bearing manufacturer, the Schaeffler Group, had made what German media reports say was a more than 10 billion-euro ($15.9 billion) bid for the company.

Continental's confirmation that it had held talks with the family- led Schaeffler group sent the tire maker's shares up by 25.02 percent to 67.46 euros on the Frankfurt stock exchange, while the Dax index of German blue-chips was up by 1.21 percent overall.

Continental awaiting firm offer

Continental said in a statement that "one brief conversation about a possible engagement by Schaeffler Group in Continental took place at the end of last week," and added: "No further conversations took place."

The statement said that "as soon as Schaeffler Group has substantiated its plans," Continental management would "evaluate these and communicate its views."

Continental has lost roughly half of its stock market value in the past year, falling below nine billion euros on Friday, July 11.

A study by Merrill Lynch pushed the share price lower last week, saying that Continental was penalized by heavy debt and high costs for raw materials.