The Trump administration has declared that its relief efforts in Puerto Rico are succeeding, but people on the island said help was scarce eight days after Hurricane Maria devastated the US territory.

The US president waived US federal restrictions on foreign ships' transport of cargo to hurricane-ravaged Puerto Rico.

Puerto Rican officials could not reach more than half their towns amid a push to evacuate tens of thousands of people over a failing dam as the disaster wrought by Hurricane Maria becomes clear.

A failing dam has sparked emergency evacuations of two towns in north-west Puerto Rico as the US territory struggled with flooding, an island-wide blackout and other dangers in Hurricane Maria's wake.

Heavy rain and 185 mph winds lashed the Virgin Islands and Puerto Rico's north-east coast on Wednesday as Hurricane Irma roared through Caribbean islands on its way to a possible hit on South Florida.