The price hike by Mars, which did not provide an effective date, follows Hershey Co, the No. 1 candy maker in the United States, which on July 15 raised its chocolate prices about 8 percent due to soaring commodity costs.

"In the three years since our last price increase, in March 2011, we have invested significantly in the category and have experienced a dramatic increase in our costs of doing business," a spokesperson said in an email to Reuters.

Mars Chocolate North America is a subsidiary of Mars Inc, the third biggest confectionery business globally next to Butterfinger-maker Nestle SA and Cadbury-maker Mondelez International, according to Euromonitor International.

The cost of cocoa, a key ingredient in chocolate, has seen a meteoric rise in the past year, having climbed nearly 50 percent to a three-year high on Wednesday at $3,204 per tonne on ICE Futures. U.S. Dairy prices have also soared.

These price increases come three months after Swiss-based Nestle SA Executive Vice President and Chief Financial Officer Wan Ling Martello said on a conference call that "there will be pricing" action in the company's confectionery business.

(Reporting by Marcy Nicholson; Editing by David Gregorio, Bernard Orr)