A man in Germany is facing a hefty bill for a night out — after his Alexa device decided to hold a party on its own while he was away.

Oliver Haberstroh claims his Amazon Alexa personal assistant started playing deafening music on its own at two in the morning without any instructions from him.

Police had to break into his Hamburg flat to switch the music off after neighbours complained about the noise.

Alexa is an “intelligent personal assistant” installed on Amazon Echo smart speakers, which enables owners to play music and control the lighting and thermostat by voice command.

It can order a taxi or a pizza delivery, and answer questions using the internet. But Mr Haberstroh claims his Alexa appears to have a mind of its own.

On Friday night, he says, he went out leaving his flat empty and the music switched off.

“While I was relaxed and enjoying a beer, Alexa managed on her own, without command and without me using my mobile phone, to switch on at full volume and have her own party in my apartment,” he wrote on Facebook. “She decided to have it at a very inconvenient time, between 1.50am and 3.00am. My neighbours called the police.”