One person was swept away and 4,000 were displaced Saturday when heavy rains from a newly forming tropical depression slammed into the Dominican Republic, authorities said, warning the Bahamas was next.

Alfonso Astacio was trying to cross a river in a van in Hato Mayor, some 110 kilometers (70 miles) northeast of the capital, and was swept away in the torrent, said Juan Manuel Mendez, director of the country's emergency operations center.

Flooding near rivers and in cities also damaged more than 800 homes and cut off 23 towns, the emergency center said in its latest update. Some 4,105 people went to take refuge in the homes of family and friends, it added.

A hospital in the country's east, where the rains were heaviest, also experienced flooding on the ground floor and "patients were moving to dry places," the bulletin said.

After passing the Dominican Republic, the storm strengthened further and was dubbed Tropical Depression Four.

It was moving towards the southeastern Bahamas, the National Hurricane Center said in its 0300 GMT bulletin, and forecast to strengthen into a tropical storm by Sunday.

A tropical storm warning was in effect for much of the southeastern and central Bahamas as well as for the Turks and Caicos islands, the Miami-based center said.

It warned the torrential downpours could produce life-threatening flash floods and mudslides, especially in areas of mountainous terrain, adding that the areas under threat would spread northward along the storm's path.