Volkswagen CEO Martin Winterkorn has fueled buzz about who will be his successor when he retires with comments about recent recruitments and hints that the possibilities are open.

Winterkorn, who is planning to retire next year, said hiring executives from Daimler and BMW in 2014 sparked discussion about potential successors to the chief executive throne, the Wall Street Journal reported.

Andreas Renschler, formerly of Daimler, and Herbert Diess, who was recruited from BMW, are the two recent additions to Volkswagen who are being viewed as CEO material. Renschler, who began this month, was brought on to head VW's truck business and to make the commercial vehicle division a global contender, while Diess will step in to lead the VW brand later this year.

"Both colleagues are executives who have done well in their previous companies," Winterkorn said in an interview that will be published soon in the German news magazine Stern. "Otherwise we wouldn't have hired them."

But Winterkorn didn't comment on speculation about internal hires and said VW has plenty of options for a strong replacement CEO.

"There are many here who could do just as good a job," he said.

As for qualifications, Winterkorn said VW's new CEO doesn't have to be an engineer, but it would be useful since the automaker puts a new model on the market every two weeks on average.

The new VW chief "must have great affinity to our products," Winterkorn said.

"As always, it depends on the person. But the decision about who will be my successor will certainly not be an easy one for the supervisory board," Winterkorn told Stern.

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