A helicopter crashed into the Cairns hotel shortly before 2am on Monday. [Source: ABC]

Hundreds of people have been evacuated after a helicopter crashed into the roof of a Far North Queensland hotel this morning.

Police have declared an emergency around the building on Cairns Esplanade and evacuated up to 400 people after the crash which happened shortly before 2am, a Queensland Ambulance Service (QAS) spokeswoman said.

Two of the helicopter’s propellers came off and landed on the esplanade and in the hotel pool.

The crash has been described as sounding like a “bomb”.

“It is quite frightening to hear, that noise of a helicopter crashing,” QAS senior operations supervisor Caitlin Denning said.

“There’s been reports it sounded like a bomb, and seeing smoke and fire from that, a lot of the occupants of the hotel were very unsure about the situation at the time.

“There is a lot of unease at the evacuation centre.”

Two people in the building were taken to Cairns Hospital in a stable condition.

It’s unknown how many people were in the helicopter, or their condition.

Hotel guests have been evacuated to a nearby hotel.