Google Inc promoted a daily deals offer on the front page of its website on Wednesday, a rare instance of the search giant using the prized online real estate for advertising.

Google, the world's No.1 Internet search engine, launched a daily deals business in certain cities earlier this year, in a move to counter the increasing influence of deals giant Groupon.

The move signals an escalation of Google's competition with Groupon, as the two companies vie for ad dollars from local businesses, such as restaurants and retail stores.

A short blurb underneath Google's famously sparse homepage on Wednesday offered visitors $25 tickets to New York's American Museum of Natural History for the discounted price of $5.

Google has traditionally resisted using its homepage for ads in the past, save for occasionally promoting in-house products such as its Chrome Web browser.

Google generated 96 percent of its roughly $29 billion in revenue last year from advertising. Most of it comes from ads that appear alongside Google's search results.

Google was not immediately available for comment.

(Reporting by Alexei Oreskovic and Alistair Barr; Editing by Tim Dobbyn)