A plane has crashed into the sea near a popular beach town in Thailand - killing at least five people on board. Five of the six police officers have died, whilst the condition of one person on board remains unknown.

The small aircraft plunged into the Gulf of Thailand off the coast of Cha-am off in the southwest of the country at around 8.25am local time (2.25am in UK). The Cha-am district is popular for weekend getaways and is just 80 miles from the capital. Authorities said the plane, operated by the Police Aviation Division, crashed just miniutes after taking off. 

The plane was pictured nosediving into the water while on a test flight to prepare for parachute training in Hua Hin district, said Royal Thai Police spokesperson Archayon Kraithong.

The Royal Thai Police expressed its "deepest condolences and sympathy" to the victims of the crash.

Photos from the scene show the body of the plane appearing to be broken in two with the aircraft around 100m offshore.

Officials did not immediately share the model of the propeller plane, but photos from the scene appeared to show a Viking DHC-6 Twin Otter with images showing the fatal wreckage floating in the sea. 

The propeller plane was just over 300ft offshore at the time of the fatal plummet, says officials.

People were captured wading through chest-deep water to reach the site.

The cause of the crash is not currently known. Authorities are examining the aircraft's black box data recorder to determine the cause of crash.

Police chief Kitrat Phanphet has confirmed a full investigation is underway adding that the "families of the victims will be closely supported and funeral arrangements will be made for them". 

A spokesperson for Prachuap Khiri Khan Provincial Police said: "We are currently coordinating with relevant agencies to provide assistance because the incident occurred in the sea, far from the shore, which makes it difficult to provide assistance. If there are any further details, we will report them."