Miami, Florida  - Tropical Storm Paloma strengthened into a hurricane in the Caribbean Sea as it headed toward the Cayman Islands, the National Hurricane Center in the United States said.

Paloma had maximum sustained winds of 120 kilometres per hour by late Thursday, making it a category one hurricane on the five-level Saffir-Simpson scale.

The Miami-based centre said it was expected to strengthen further and forecast that it would reach category two status Friday when it was expected to reach the Caymans and possibly hit category three by Saturday.

On Sunday, it was forecast to hit Cuba, which has already been pummeled by two hurricanes this season.

A hurricane warning was issued for the Cayman Islands, and residents there were warned to rush preparations to protect their lives and property.

By late Thursday, Paloma was located 240 kilometres south-south-west of Grand Cayman Island and 435 kilometres west-south-west of Montego Bay, Jamaica. It was moving northward at 19 kilometres per hour, the storm centre said. (dpa)