France's competition authority has fined Google €150 million for abusing its dominant position on the market for advertising linked to web searches, the regulator announced Friday.

The authority, in its first-ever sanctioning of the American giant, also ordered Google to "clarify the operating rules of its Google Ads advertising platform and the procedures for suspending the accounts" of certain advertisers.

The move was the third biggest penalty ever handed out for abuse of market dominance by the authority, its chief Isabelle de Silva told a news conference.

Google holds an "extraordinarily dominant position" in search-based advertising, with a market share of between 90 and 100 percent, she said, and "when you have great power, you also have great responsibilities".

She said the authority had no argument with Google establishing rules for access to its search-based ad services, but "these rules must be clear".

Google could not be allowed to apply rules in "an erratic way".

Uncertainty about the rules framework for advertisers "may have discouraged the development of innovative sites", the competition authority said.

Google has two months to produce a detailed proposal of measures and procedures it intends to implement to bring its practices into line, it said.