MANILA, Philippines (AP) _ Tropical storm Brenda gained strength as it neared the central Philippines on Tuesday, forcing authorities to post storm warnings in 20 provinces and stop six ships from leaving Manila.

Brenda, packing winds of 53 mph, was about 270 miles southeast of the town of Borongan on Samar island, about 370 miles southeast of Manila. It was moving west-northwest at 9 mph.

If Brenda maintains its present speed, it will hit Leyte island Wednesday with gusts of up to 63 mph, weather officials said.

The Philippine coast guard station in Manila kept six commercial ships in port. In October, the passenger ship Dona Marilyn sank in the central Visayan Sea during a typhoon and more than 300 people died.

Authorities at the U.S.-run Subic Bay Naval Base, Cubi Point Naval Station and San Miguel Communication Station also raised storm warnings on base.