Rain and wind hit a parking lot at Roberto Clemente Coliseum in San Juan, Puerto Rico. Picture: Hector Retamal/AFP

San Juan, Puerto Rico - Hurricane Maria slammed into Puerto Rico on Wednesday as the strongest storm to hit the US territory in nearly 90 years, ripping windows from their fixtures and sending debris hurtling through the streets as it approached the capital, San Juan.

Maria, the second major hurricane to roar through the Caribbean this month, made landfall near Yabucoa, on the southwest coast of the island of 3.4 million people. Thousands of people were seeking safety in shelters.

Carrying winds of 233km/h and driving high storm surges, Maria's eye was located about 25km southwest of San Juan at 9am ET (1300 GMT), the US National Hurricane Center said.

Trees are toppled in a parking lot at Roberto Clemente Coliseum in San Juan, Puerto Rico. Picture: Hector Retamal/AFP

Buildings trembled as the storm battered San Juan and sent torn off pieces of metal barricades clattering along streets.

Broken windows, mangled awnings and gutters dangled haphazardly from buildings or were ripped off entirely. Toilets bubbled noisily and belched foul air as the hurricane rumbled through the city's water and sewage lines.

On its passage through the Caribbean, Maria killed at least one person in the French territory of Guadeloupe and devastated the tiny island nation of Dominica.

Hurricane Irma, which ranked as one of the most powerful Atlantic storms on record, also left a trail of destruction in several Caribbean islands and Florida this month, killing at least 84 people in the Caribbean and the US mainland.

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

"Although it looks like a direct hit with major damage to Puerto Rico is inevitable, I ask for America’s prayers," he said, adding the government had set up 500 shelters.

Maria was expected to dump as much as 66cm of rain on parts of Puerto Rico, the NHC said. Storm surges, when hurricanes push ocean water dangerously over normal levels, could be up to 9 feet (2.7 metres). The heavy rainfall could cause life-threatening flash floods and mudslides, it added.

"This a catastrophe we're going through," said Madeline Morales, 62, a saleswoman in San Juan who abandoned her coastal home before the storm hit to seek refuge in a hotel on higher ground.

Maria was set to be the strongest hurricane to hit Puerto Rico since 1928, when the San Felipe Segundo hurricane slammed the island and killed about 300 people, the National Weather Service said.

Before hitting Puerto Rico, Maria passed west of St. Croix, home to about half of the US Virgin Islands' 103,000 residents, as a rare Category 5 storm, the top of the five-step Saffir-Simpson scale. Authorities expected to start assessing storm damage on St. Croix from daybreak.

Maria was on a track to pass just north of the northeast coast of the Dominican Republic on Wednesday night and Thursday, the NHC said. So far, it did not look likely to threaten the continental United States.

This, GOES-16 satellite image taken on Tuesday and provided by National Oceanic and Atmospheric Administration (NOAA), shows Hurricane Maria southeast of Puerto Rico. Picture: NOAA via AP

"This is going to be catastrophic for our island," said Grisele Cruz, who was staying at a shelter in the southeastern city of Guayama. "We're going to be without services for a long time."

Irma grazed north of Puerto Rico but did not hit the island directly. But it storm knocked out power for 70 percent of the island, and killed at least three people.

Puerto Rico is grappling with the largest municipal debt crisis in US history, with both its government and the public utility having filed for bankruptcy protection amid disputes with creditors.

Maria plowed into Dominica, a mountainous country of 72,000 people, late on Monday causing what Prime Minister Roosevelt Skerrit called "mind-boggling" destruction.

North of Dominica, the French island territory of Guadeloupe appeared to have been hit hard. The Guadeloupe prefecture said one person was killed by a falling tree and at least two people were missing in a shipwreck.

Some roofs had been ripped off, roads were blocked by fallen trees, 80,000 households were without power and there was flooding in some southern coastal areas, the prefecture said in Twitter posts.

There were hurricane warnings and watches in effect for the U.S. and British Virgin Islands, Puerto Rico, Culebra, and Vieques, the Turks and Caicos Islands, the southeastern Bahamas and the Dominican Republic from Cabo Engano to Puerto Plata.