Hurricane Humberto gained strength early Tuesday, packing 90 mph (150 kph) winds and it was expected to become a major hurricane with 111 mph (178 kph) winds by Tuesday night or early Wednesday as it tracks towards Bermuda, forecasters said.

Bermuda could be hit with tropical-storm-force winds and up to 3 inches of rain by late Wednesday, the Miami-based National Hurricane Center (NHC) said in an advisory.

The centre of the hurricane is expected to approach Bermuda Wednesday night, the NHC said, and current tracks show it sideswiping Bermuda's west coast Thursday.

Humberto was 595 miles (960 km) west of Bermuda, picking up speed and moving at 8 mph (13 kph), the forecasters said.

Humberto, which gained hurricane strength late Sunday, dropped another 2 inches of rain on the storm-ravaged northwestern Bahamas as it churned away from the US coast, the NHC said.

It is bringing life-threatening waves and tides to parts of the US east coast from Central Florida to North Carolina and dangerous conditions will remain for the next few days, forecasters said.