EU regulators are investigating Google for Jobs to see if the company unfairly favors its fast-growing tool for searching job listings, Europe's antitrust chief said.

Launched two years ago, the tool has already drawn numerous complaints from rivals alleging anti-competitive behavior.

Earlier this month, 23 job-search websites in Europe urged the European Commission to temporarily order Google to stop such practices while it investigates the issue.

European Competition Commissioner Margrethe Vestager, who has handed out 8.25 billion euros ($9.2 billion) in fines to the tech giant in recent years over three separate cases, voiced concerns about the possibility of similar anti-competitive practices by Alphabet unit Google in other areas.

"We're looking right now at whether the same thing may have happened with other parts of Google's business - like the job search business known as Google for Jobs," Vestager told a conference in Berlin.

Google said that it had made changes to the tool following feedback in Europe, including offering direct links to a choice of job sites and linking directly to job offers available only on a single site.

Vestager noted that the European Commission may adopt rules to rein in tech giants if the firms do not play fairly.

"There's also a broader issue for our societies, of whether we think it's right for companies like Google and others to have such control over the success or failure of other companies, and be free to use that power in any way they like," she said. 

"If we don't, then we may find that we need regulation, to make sure that these platforms use their power in a way that's fair and doesn't discriminate," Vestager said.