Hurricane Maria has knocked out power to the entire island of Puerto Rico, home to 3.5m people, emergency officials have said.
Abner Gómez, head of the disaster management agency, said the hurricane had damaged “everything in its path”.
None of the customers of Puerto Rico’s Electric Power Authority had any electricity, he said.
Maria weakened to a category three storm with winds of 115 mph (185km/h) as it moved across the island.
“The information we received is not encouraging,” Mr Gómez told a briefing, urging people to stay in their homes.
Earlier, Puerto Rico’s governor asked President Donald Trump to declare the island a disaster area after the storm unleashed heavy flooding and life-threatening winds.Governor Ricardo Rossello said major damage was inevitable, although 500 shelters had been established to protect people.
The devastating storm has already left seven people dead on the island of Dominica, which was badly affected on Monday.
Aerial footage shows flattened houses and the death toll on Dominica is likely to rise, with details remaining scant as communication links are down.
Images shared on social media show roofs being stripped away as winds as strong as 140 mph (225 km/h) whipped trees and power lines in Puerto Rico’s capital city, San Juan.
Maria made landfall in Yabucoa in the east of Puerto Rico early on Wednesday, according to the US National Hurricane Center (NHC).
The US territory is facing $73bn in public debt and the damage left by Maria could exacerbate its financial crisis. Declaring a disaster would mean the island could receive more federal assistance in its recovery.
“God is with us; we are stronger than any hurricane,” Mr Rossello said. “Together we will rise again.”
Puerto Rico has experienced just one category five storm since 1851 – the Okeechobee Hurricane in 1928.
Maria is the second storm of this strength to hit the Caribbean this hurricane season – the first being category five Irma earlier in September. Maria began moving roughly along the same track as Irma.
Officials in Puerto Rico feared the debris left by Irma could prove extremely dangerous in the high winds.