Five people are dead and several still missing after two seaplanes have collided in mid-air over south-eastern Alaska.

Ten people were also injured when the two sightseeing planes went down over water about 40-48 kilometres north-east of Ketchikan, the US Coast Guard and Federal Aviation Administration officials said.

The crash site, which the FAA said was at Coon Cove near George Inlet, is near a popular tourist lodge that runs excursions to the nearby Misty Fjords National Monument. The monument is about 480 kilometres south of Alaska’s capital, Juneau.

One of the planes was carrying 11 passengers and crew, the other had five people aboard. It was initially reported that 10 people were receiving medical care, with six others unaccounted for.

Later it was confirmed three of the missing had been killed. PeaceHealth Ketchikan Medical Centre spokesman Marty West said all the patients were in fair or good condition.

#breaking: Princess Cruises says 5 people are dead, including 4 Royal Princess guests and pilot after Taquan float plane crashed about 8 nautical miles from Ketchikan, Alaska. The plane was flying a shore excursion sold through Princess Cruises.

Princess Cruises Statement below. pic.twitter.com/CTssjYrJIA

— Preston Phillips 🇺🇸 (@PrestonTVNews) May 14, 2019

The plane passengers were from cruise ship Royal Princess and were on sightseeing flights, one which was operated by Taquan Air.

Princess Cruises later confirmed in a statement that four of its passengers and a Taquan pilot had been killed.

A Taquan spokeswoman told The Associated Press the company had suspended operations while federal authorities investigated the deadly crash.

“We are devastated by today’s incident and our hearts go out to our passengers and their families,” the company said in a statement.

“At this time, we are in the midst of an active crisis response, and our focus is on assisting these passengers, the pilot, our staff, their families and loved ones, and first responders.”

Cindy Cicchetti, a passenger on the Royal Princess, told the AP that the ship’s captain had announced news of the tragedy. The ship had been scheduled to sail on from the area and arrive in Anchorage on Saturday, but it was not leaving yet, she said.

Neither of the single-engine planes was under air traffic control when they collided, and circumstances of the crash were not immediately known.

-with agencies