Hurricane Gustav had gathered strength early Tuesday in the Caribbean Sea and was threatening Haiti, the Dominican Republic, Cuba and Jamaica, forecasters said. According to DPA , Gustav could produce 10 to 20 centimetres of rain over Hispaniola, eastern Cuba and Jamaica, with some areas receiving up to 50 centimetres, the US National Hurricane Centre in Miami said. "These rains will likely produce life-threatening flash floods and mud slides," its latest report said. The NHC said Gustav formed unexpectedly early Tuesday, south of the island of Hispaniola (the second-largest and most populous island of the Antilles ), where the countries of Haiti and the Dominican Republic are located. It has maximum sustained winds of 150 kilometres per hour. The category 1 hurricane on the five-level Saffir-Simpson scale was expected to move over south-western Haiti later Tuesday and near eastern Cuba on Wednesday. The hurricane had already caused heavy rain and strong winds in Haiti and the Dominican Republic by Tuesday. The authorities of both countries decreed maximum alert levels in the affected areas, where flooding, flash floods and mudslides were feared. Some 4,360 people had to be evacuated and more than 870 homes suffered damage in the Dominican Republic. Emergency services in the country said no one had been reported dead in connection with the hurricane.