UPDATE 1-Venezuela quarantines cruise ship over flu scare

* Barbados, Grenada rebuff cruise ship over flu scare

* Ship in quarantine in Venezuela, 3 H1N1 cases confirmed

* Cruise industry economic mainstay for Caribbean states (Updates with ship in Venezuela, 3 cases confirmed)

CARACAS, June 17 (Reuters) - Venezuela quarantined a Spanish cruise ship on Wednesday after three crew members were diagnosed with the H1N1 flu virus and Barbados and Grenada refused to allow its passengers to disembark.

The cruise ship, owned by Royal Caribbean Cruises (RCL.N: Quote, Profile, Research), is docked off the Venezuelan island of Margarita and the 1,200 people aboard will not be allowed off for a week, Venezuelan officials said.

"The virus was detected in three crew members and the boat must now stay in quarantine until June 24," state health official Jorge Alchaer said in comments printed by the government news service.

On Monday, the Ocean Dream operated by Pullmantur Cruises docked in Grenada, but no one was permitted to leave the ship because of reports several people on board had flu-like symptoms, a spokesman for Grenada's Health Ministry said.

The cruise liner's next destination was Barbados on Tuesday, but the ship was not allowed to berth by Barbadian authorities, shipping agents in Bridgetown said.

Miami-based Royal Caribbean, which owns Pullmantur, said it could not comment on the situation. Pullmantur representatives were not immediately available for comment.