Yahoo has been issued a subpoena in a New York state investigation into daily fantasy sports games, sources close to the case said Thursday.

The latest action clouds Yahoo's fantasy sports operations amid a legal battle by the office of the state's attorney general to shut down two other services, DraftKings and FanDuel.

"We can confirm that a subpoena was issued to Yahoo last week," the source told AFP.

Attorney general Eric Schneiderman's office is seeking details on Yahoo Sports Daily Fantasy, which operates in 43 US states.

Like other fantasy sports sites, Yahoo allows participants to select players for a virtual "team" and then use the real-world performance of the athletes to win prizes.

New York state officials are seeking separate court orders to shut down fantasy sports websites DraftKings and FanDuel, claiming they are in fact gambling operations illegal under state law.

Schneiderman issued an administrative cease-and-desist order on November 11 following an investigation by his office concluding the two websites are illegal gambling operations.

The companies say they are games of skill rather than gambling operations. But the two firms shut down operations in Nevada following a similar investigation.

Yahoo said in a statement earlier this week it does not comment on legal matters but noted: "We are monitoring industry trends and events closely and believe that we offer a lawful product for our Daily Fantasy Sports users."