Relief agencies are working to deliver food and supplies over flooded roads and piles of debris, after Hurricane Dorian hit the Bahamas on September 1.

The Royal Bahamas Police Force said at least 45 people died the Bahamas as the fierce storm tossed cars and planes around like toys. The death toll is likely climb.

Dorian was one of the most powerful Caribbean storms on record, a Category 5 hurricane with winds of 320km/h.

It rampaged over the Bahamas for nearly two days, becoming the worst disaster in the nation's history.

Large swaths of Greater Abaco Island were destroyed.

One Bahamian rescue worker said it was becoming hard to keep composed when surrounded by death.

"If you're not in touch with yourself then you lose it. You have to be mentally stable because when you're seeing these things, and when people who lost loves ones are crying on your shoulder you can't break down on them," said one hazmat-suited Bahamian police office who could not give his name.

"These families need this, they need someone to talk to."

Bahamian officials said 4800 people had been evacuated from the archipelago's several islands, most from Abaco.

Free flights will continue to evacuate people who choose to leave the Bahamas, but there are no mandatory evacuations, officials said.

"The plan is not to move everyone out," National Emergency Management Agency spokesman Carl Smith told a news conference on Monday.

Thousands of people poured into the capital Nassau, where a week after the storm shelters were straining to house evacuees from worse-hit areas.

Hundreds more have fled to the US in search of safety and resources.

Shelters are housing about 1100 people, the agency said; more are staying with friends and relatives.

The agency was asking residents whose homes were intact to open them up to people displaced by the storm.

Some 90 per cent of the homes, buildings and infrastructure in Marsh Harbour were damaged, the World Food Programme said.

Thousands of people were living in a government building, a medical centre and an Anglican church that survived the storms, it said, but had little or no access to water, power and sanitary facilities.

Some 70,000 people were in need of food and shelter, the WFP estimated.

Private forecasters estimated that some $US3 billion in insured property was destroyed or damaged in the Caribbean.

Australian Associated Press