Some hard hit areas of the Northern Marianas could be without power and water for weeks after the Pacific Ocean islands were battered by a super typhoon, an official has said.

The only hospital on Saipan, a US territory that is the largest of the Mariana Islands, experienced severe flooding and on Thursday there had been reports of big resorts losing backup generators, said Ed Propst, a former lawmaker who works in the governor’s office.

“It’s pretty bad conditions right now,” he said, adding that people were bracing for a long stretch without electricity and water.

Super Typhoon Sinlaku first hit the islands on Tuesday night and continued into Wednesday, with a barrage of fierce winds and relentless rains that flipped over cars, toppled utility poles and ripped away tin roofs. Authorities were just beginning to assess the damage left behind by the storm.

Power and water were out and many of the roads impassable across Saipan and Tinian in the Northern Mariana Islands, home to about 45,000 people, according to officials.

In a text to the Associated Press, Bernard Villagomez, a public information officer for the territory, said: “We still have a shelter in place so first responders have not been able to do a full damage assessment.”

The storm also battered Guam, another US territory and the site of several American military bases, with tropical force winds.

The typhoon had sustained winds of up to 150mph (241km/h) when it made landfall, the national weather service said, and on Wednesday, was packing winds of 125mph as it pulled away to the north from the islands of Saipan, Tinian and Rota. Sinlaku is expected to start curving toward sparsely populated volcanic islands in the far northern Marianas.

The storm was about 170 miles north-west of Saipan on Thursday, the weather service said. Many sensors on the island were down, but it estimated that winds were about 60 to 70mph.

Mathew Masga, a resident, said the winds had made it unsafe to go outside but some stores were open on Tinian on Thursday and people were rushing to purchase supplies.

“While driving around, I noticed numerous wooden and semi-concrete houses with damaged rooftops due to the passing typhoon,” he said in a Facebook message. “Notably, many of our power poles and power lines are down.”