Rescue teams are still struggling to reach some flood-hit Bahamian communities in the aftermath of Hurricane Dorian as top officials said the death toll had risen to 43, while it is feared hundreds, perhaps thousands, remain missing.

Government agencies and charities continued to bring desperately needed relief efforts to the Bahamas, including cruise ships loaded with supplies and volunteers.

The Bahamian prime minister, Hubert Minnis, updated the death toll late on Friday but warned that the number was “expected to increase significantly”. “This is one of the stark realities we are facing in our darkest hour,” Minnis said in a statement.

Play Video 1:40 ‘The seas came up to our doors’: Hurricane Dorian leaves trail of destruction in Bahamas – video

“The loss of life we are experiencing is catastrophic and devastating. The grief we will bear as a country begins with the families who have lost loved ones. We will meet them in this time of sorrow with open arms and walk by their sides every step of the way.”

Thirty-five of the official deaths were in the Abaco Islands and eight in Grand Bahama.

Marvin Dames, the security minister, said authorities were striving to reach everyone, but the crews could not just bulldoze their way through fallen trees and other rubble because there might be bodies not yet recovered. “We have been through this before, but not at this level of devastation,” Dames said.

The town turned to rubble by Hurricane Dorian – in pictures Read more

The United Nations has estimated 70,000 people were in “immediate need of life-saving assistance” such as food, water and shelter.

Hundreds of desperate storm victims gathered on Friday at the port on Grand Abaco in hopes of getting off the devastated island amid signs of rising frustration over the pace of the relief effort. “It’s chaos here,” said Gee Rolle, a construction worker who waited with his wife for a boat that could take them to the capital, Nassau. “The government is trying their best, but at the same time, I don’t think they’re doing a good enough job to evacuate the people. It ain’t livable for nobody. Only animals can live here.”

‘90% of infrastructure damaged’

The World Food Programme said it had delivered 14,700 ready-to-eat meals to Nassau on Friday that would be distributed to the islands. A senior WFP spokesperson said it had a team in Abaco: “Assessments for Abaco found widespread destruction, with thousands of houses levelled, telecommunications towers down, and roads blocked; in Marsh Harbor, an estimated 90% of the infrastructure appears damaged.”

They added: “The government building, the medical centre and the Anglican church are housing thousands of displaced people – including women, young children and other vulnerable groups. Living conditions are rapidly deteriorating with limited or no water, electricity, and sanitation. With improved access (airport in Marsh Harbor newly reopened), some supplies are arriving including some minimal food and water. The needs remain enormous.

“Evacuations are slowly taking place by ferry, as hundreds of residents reportedly flee daily.”

The US was expanding its response to the disaster, with the Trump administration reportedly moving to requested airlift and logistical support from the US defense department, to back up efforts by the US Coast Guard.

On Saturday, the US Coast Guard said it has rescued 290 people in the Bahamas following Hurricane Dorian. It said that six MH-60 Jayhawk helicopters were carrying out search and rescue missions and providing logistical support, while nine coastguard cutter vessels were also helping in the area.

Dorian also hit parts of the Outer Banks Islands in North Carolina on Friday after briefly making landfall there.

Facebook Twitter Pinterest Kitchen staff on Royal Caribbean’s Mariner of the Seas help put together 10,000 relief meals, in Port Canaveral, Florida. Photograph: Joe Burbank/AP

Also on Saturday, forecasters said Hurricane Dorian was picking up strength as it approached Canada. In its latest advisory, issued before 2pm ET, the National Hurricane Center in Miami said the hurricane’s maximum sustained winds had increased to 100mph (155km/h) from 85mph (140km/h), raising it one notch from a category 1 to a category 2 storm.

Forecasters say the centre of Dorian is expected to move across central or eastern Nova Scotia late Saturday afternoon or early evening, pass near or over Prince Edward Island late on Saturday, and move to Newfoundland and Labrador on Sunday.

Hurricanes in Canada are rare in part because once the storms reach colder Canadian waters, they lose their main source of energy.