Hurricane Maria has made landfall on the US territory of Puerto Rico as a Category 4 storm after devastating several Caribbean islands.

The National Hurricane Centre said Maria landed near Yabucoa, in the east of Puerto Rico, packing winds of 250km/h and moving northwest at 16km/h.

"This is an unprecedented storm. Already I'm seeing it's the tenth-strongest hurricane of its kind," Puerto Rican Governor Ricardo Rossello told NBC's Today show.

"And it's a slow storm as well. It's going to be here in Puerto Rico for a while."

Maria is the second maximum-strength hurricane to hit the Caribbean in a month. Source: AAP

The National Weather Service said Puerto Rico's capital and largest city San Juan will experience winds of 185km/h and higher for the next two-to-three hours.

Given the furious winds and expected storm surges and floods, Rossello said that "we have a lot of houses over here that are wooden ... Those houses have no chance."

Maria is expected to dump as much as 63.5cm of rain on parts of Puerto Rico and bring storm surges, when hurricanes push ocean water dangerously over normal levels, of up to 2.74m, the NHC said.

The heavy rainfall could cause life-threatening flash floods and mudslides, it added.

"We have not experienced an event of this magnitude in our modern history," Ricardo Rossello, governor of Puerto Rico said in a televised message.

"Although it looks like a direct hit with major damage to Puerto Rico is inevitable, I ask for America's prayers."

Puerto Rico, a US territory of about 3.4 million people, avoided a direct hit from Irma, but the storm knocked out power for 70 per cent of the island, and killed at least three people. Maria promises to be worse.

The storm has already lashed the Caribbean, causing one death on Guadeloupe and widespread destruction on Dominica.

About 80,000 homes lost power in Guadeloupe.

There are reports of flooding, mudslides and power outages in parts of St Lucia.