An Atlantic tropical storm became a hurricane Sunday as it took aim at the eastern Caribbean, forecasters said.

Hurricane Earl was to reach the Leeward Islands at the edge of the Caribbean late Sunday or early Monday, the US National Hurricane Centre in Miami said.

Hurricane warnings were in place for the islands of Antigua, Barbuda, Montserrat, Saint Kitts, Nevis, Anguilla, Saint Martin, Saint Barthelemy, Saba, Saint Eustatius and the British Virgin Islands. The US Virgin Islands and Puerto Rico were under a hurricane watch.

Earl was a category one storm on the Saffir-Simpson scale of hurricane strength with sustained winds of 140 km per hour, but was expected to strengthen and become a major hurricane Monday, the hurricane centre said.

Meanwhile, a separate storm, Hurricane Danielle, was continuing to bring strong surf to the Atlantic islands of Bermuda. The category one storm was forecast to weaken in the next 48 hours.