Six people have died and thousands are without power or cell phone service due to "apocalyptic" wildfires in Hawaii.

Several blazes are burning on the Big Island, also known as Hawaii, and Maui, a neighbouring island.

Officials confirmed the fatalities on Wednesday and said search and rescue is still ongoing.

Authorities have evacuated neighbourhoods, closed roads, and opened five new shelters to host thousands of evacuees.

"We have shelters that are overrun, we have resources that are being taxed, we are doing whatever we can" for local residents, the state's Lieutenant Governor Sylvia Luke said during a news briefing.

An emergency order has been signed discouraging people from coming to Maui, which is a popular tourist destination.

On Maui, about 4,000 visitors are trying to leave the island, said state transportation official Ed Sniffen.

Thousands there are also without cell service, due to about 29 power poles collapsing. The full scale of the damages to homes and businesses is not yet clear, officials said.

Maj Gen Kenneth S Hara, who is in charge of the emergency response, said the priority at the moment is "saving lives, preventing human suffering, and mitigating great property loss".

More than 12,000 people in the state of Hawaii are currently without power, according to PowerOutage.

Much of the destruction has taken place in the Maui island town of Lahaina. Parts of the town were destroyed or severely damaged by the blaze.

The US Coast Guard said it had rescued 12 people after reports of residents fleeing into the water to escape the fires.

Maui County Mayor Richard Missen confirmed the six fatalities but said he was not yet able to provide further details. There were also some injuries, including a firefighter who suffered smoke inhalation.

He warned the total number of fatalities could rise as emergency responders conduct search and rescue efforts as well as evacuations.

An unknown number of residents have been treated for burn injuries and smoke inhalation at local hospitals.

The Lahaina fire is one of at least seven ongoing in Hawaii. About 13,000 people live in the city situated on the western part of the island of Maui.

Local resident, Dustin Kaleiopu, told Hawaii News Now that his house was among those destroyed in the fire.

"Everything that we'd ever known was gone. Our church, our schools, every single memory we had on this household," he said. "Everything was gone in the blink of an eye."

The fire in Lahaina is one of several in Hawaii fuelled by strong winds by Hurricane Dora hundreds of miles offshore, low humidity and dry air, according to the National Weather Service's Honolulu office.

Local officials have said that the winds have complicated efforts to use helicopters for firefighting operations.

As of Wednesday morning, all public schools in Maui were closed except one.

On Tuesday night, Ms Luke issued an emergency declaration and activated the state's National Guard.

Fires in Hawaii are typically smaller than those which plague California and other parts of the western continental US.

Experts have warned, however, that they are often more damaging, as Hawaii's ecosystem evolved without fires before the arrival of humans and can remove vegetation.