Howling winds and lashing rains battered Guam and the Northern Mariana Islands as super typhoon Bavi made landfall on Monday.
Bavi brought wind speeds of 290km/h (180mph) as it moved over the island of Rota, according to the US National Weather Service (NWS).
The NWS warned the "very dangerous" storm could cause "catastrophic" damage, with waves potentially nearly 11m (35ft) high. An official told AFP they had received reports of "major damages" on the Northern Mariana Islands.
Bavi headed west over the Philippine Sea in the early hours of Tuesday morning, and Guam officials announced they would conduct initial damage assessments at first light.
Even as it headed into open water, Guam's Joint Information Center warned that Bavi could maintain wind speeds of up to 165 mph and cause tropical-storm force winds to extend outwards as far as 320 miles from its centre.
The islands of Guam, Rota, Tinian and Saipan remain under coastal flood and high surf alerts, as the NWS warned of "dangerously large breaking waves" up to 25ft (7.6m) high.
The Guam Waterworks Authority (GWA) reported 28 of the island's 99 water wells remained offline after the storm.
Beginning at 06:00 local time on Tuesday, the Joint Region Mariana - the US military command for Guam and the Mariana Islands -- would enter into an active recovery phase by deploying emergency resources and scouting teams.
Guam Governor Lourdes A Leon Guerrero and his deputies would also begin damage assessments on Tuesday morning, Joint Region Mariana announced.
The western Pacific region is particularly prone to tropical cyclones. While storms of this strength are unusual for the US islands, scientists say climate change is making powerful typhoons more common.
Residents in the region moved to emergency shelters and making last-minute preparations before the arrival of the super typhoon.
In the Northern Mariana Islands, Rota - the southernmost inhabited island, about 50km north-east of Guam - took a direct hit, according to the NWS.
The mayor's office published an advisory urging residents to prepare for "destructive winds", adding that "conditions are expected to deteriorate rapidly, making it unsafe to be outdoors".
"We are hanging in there. We are experiencing heavy winds and flooding," a spokesperson for Rota's mayor told AFP, adding that some people had reported "major damages".
On Saipan, north of Rota, wind gusts of more than 161km/h (100 mph) were recorded at the airport, meteorologist Marcus Landon Aydlett told the Associated Press.
He added that many people on the island were already without power from the last super typhoon Sinlaku, which hit Guam and the Northern Mariana Islands in April - killing 17 people and causing about $1.5bn (£1.1bn) in damage.
The NWS also warned that winds are not forecast to fall below typhoon force until early afternoon on Monday, and below tropical storm force until after midnight.
Guam, usually a sun-soaked tourist destination with a population of about 170,000, has opened five evacuation centres in its schools. The sites have a maximum capacity of about 1,700 people, and are primarily intended for the most vulnerable residents.
By 13:00 local time on Sunday one of the evacuation sites had already reached maximum capacity, the island's civil defence office said.
Bavi was classified as a super typhoon by the Joint Typhoon Warning Center (JTWC), a part of the US military responsible for monitoring tropical storms in the western Pacific.
A super typhoon has winds in excess of 240km/h. The NWS considers super typhoons to have the equivalent destructive potential as a category four or five hurricane.
Pinky Cubacub, 55, told news agency AFP that she had been boarding up the windows of her eatery in Guam with $500 (£373) worth of plywood.
"I cannot afford to lose so many days. It hurts," she said. "Because I just started, whatever we're making right now is just for rent, utilities, and my people, and supplies. I don't even pay myself yet."
Japanese tourist Miku Sakurai, 25, told AFP that her return flight to Tokyo on Sunday was cancelled.
"We will stay in the hotel when the storm comes. I am scared," she said.
Bavi will be the 11th category four or five tropical cyclone to hit US territory in the past decade, one more than the total recorded in the prior 57 years.
A strong El Niño event - a periodic warming of an area of surface water in the Pacific that contributes to weather patterns - is expected to push more tropical storms to higher intensities.
Warmer sea surface temperatures drive more moisture into the atmosphere, supercharging storms.
Source: BBC
--Agencies
