Authorities in Haiti called Tuesday for evacuations as Tropical Storm Emily threatened to bring flash floods to the impoverished nation struggling to recover from a devastating earthquake.

A tropical storm warning was in effect for Haiti as well as its neighbor on the island of Hispaniola, the Dominican Republic, and for the US territory of Puerto Rico, the US National Hurricane Center said.

Haiti's weather service chief Ronald Semelfort said heavy rains could start pounding the country late Wednesday, warning this "represents a great danger for the country still fragile from the January 2010 earthquake."

Tens of thousands of Haitians remain in makeshift camps more than 18 months after the quake, which killed an estimated 225,000 people.

Authorities were spreading the word and "are asking people in refugee camps... to evacuate vulnerable locations," said Alta Jean-Baptiste, head of Haiti's civil defense.

"We will review this evacuation strategy based on the probability of damage from the storm," he added.

The Miami-based Hurricane Center warned heavy rain from Emily could trigger deadly flash-floods in Haiti, the Dominican Republic and Puerto Rico.

Emily is currently forecast to drop between four and six inches of rain on Hispaniola and Puerto Rico, "with isolated maximum amounts of 10 inches possible," the NHC said.

"These rains could cause life-threatening flash floods and mudslides in areas of mountainous terrain," the NHC said. Haiti has in the past witnessed dozens of deadly landslides with many of the hills which surround the capital stripped bare of trees.

At 1800 GMT, Emily was some 215 miles (345 kilometers) south-east of San Juan, Puerto Rico, packing winds of 45 miles (70 kilometers) per hour.

A "slight strengthening is anticipated during the next day or two," the weather experts said.

The storm was moving towards the Dominican Republic and Haiti at 12 miles (19 kilometers) per hour, and on the forecast track its center "will be near the coast of Hispaniola on Wednesday," the NHC said.

The Dominican Republic declared an alert for portions of the country, called for mandatory evacuations in a dozen villages near dams and urged residents to take precautions in other areas.

"Residents in high-risk areas, who live next to rivers, streams and creeks... should take precautions and be aware of the recommendations of the relief agencies," the government's office of emergency services said.