LAS VEGAS - Nevada regulators have ordered daily fantasy sports sites like DraftKings and FanDuel to shut down, saying they can't operate in the state without a gambling license.

The decision comes amid growing backlash by investigators and regulators over the sites, which have grown in popularity in the past year.

The sites insist they are skill-based games and not chance-based wagers, and are therefore not subject to gambling regulations. Customers pick daily lineups of players in professional football, basketball, hockey and more, and they compete with other players to earn the most points and win money - in some cases more than $1 million.

The state's Gaming Control Board issued a notice Thursday saying the sites must stop offering their contests to Nevada residents effective immediately. Operators face felony fines and 10 years in prison.

Regulators say the sites can apply for licenses.