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MIAMI, Sept 25 (Reuters) - Tropical Storm Kyle, the 11th of the Atlantic hurricane season, formed on Thursday from a weather system that pounded Puerto Rico and other northern Caribbean islands for days, the U.S. National Hurricane Center said.

Kyle finally gained tropical storm strength, with sustained winds 45 mph (72 kph), as it moved through the Atlantic Ocean east of the Bahamas, on a path that could take it to a landfall in Maine or Canada's maritime provinces as a minimal Category 1 hurricane.

The storm was located about 645 miles (1,038 km) south-southwest of Bermuda and was moving to the north at about 8 mph (13 kph), the Miami-based hurricane center said.

The system drenched Puerto Rico, the Virgin Islands and Hispaniola for days before moving north into the Atlantic.

Authorities in Puerto Rico said at least four people were killed and scores of homes were flooded.

Forecasters warned people in Bermuda to closely monitor the progress of the storm. Computer models indicated it could reach hurricane strength within a couple of days.

It was the first tropical storm to form in the Atlantic-Caribbean region since Tropical Storm Josephine on Sept. 2, a lengthy lull in what has been a busy and destructive hurricane season so far.

As many as 700 people were killed in impoverished Haiti when four storms, Fay, Gustav, Hanna and Ike, hit the island of Hispaniola in a month.

Gustav and Ike forced the evacuation of hundreds of thousands of people and disrupted oil and natural gas production in the Gulf of Mexico before slamming ashore in Louisiana and Texas respectively.

Forecasters had predicted the six-month season, which runs through Nov. 30, could produce up to 18 tropical storms and hurricanes.

Long-range forecasts indicated that Kyle would likely move north through the Atlantic well to the west of Bermuda and approach the U.S. state of Maine and the Canadian provinces of New Brunswick and Nova Scotia as a Category 1 hurricane on the five-step hurricane intensity scale, with winds around 75 mph (120 kph), by Sunday.

Forecasters were also watching a weather system near the North Carolina-South Carolina border that could develop into a cyclone. They said the storm was producing flooding, a heavy surf and strong rip current along parts of the U.S. east coast. (Reporting by Jim Loney, editing by Xavier Briand)

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