Sales of the 2010 Toyota Prius are booming in the U.S., up more than 50 percent over last year during April alone.

But they're way better yet in Japan, where the 2010 Prius has just completed a full year as the country's best-selling car.

Toyota sold 26,482 Prius models in Japan during April, marking its twelfth consecutive month on top of the sales charts, according to the Japan Automobile Dealers Association.

The 2010 Toyota Prius has remained popular in Japan due to government incentives for highly fuel efficient vehicles. The Prius is by far the largest car on the market to return 50 miles per gallon.

The Prius is now Toyota's third best-selling car in the U.S., after the Camry and Corolla sedans.