Amazon Echo devices. James Cook/BI BERLIN — Some Amazon Echo owners have complained that Alexa — the voice-controlled virtual assistant that sits inside the smart-home device — wasn't responding to them.

Owners vented their frustrations on Twitter early on Wednesday morning, with many of them saying that they couldn't operate other connected devices, such as lights and music systems, in the way that they usually would.

"With Alexa down, I had to open the Philips Hue app to turn off the lamp like some kind of fucking barbarian," wrote Amazon Echo owner Mark Hopkins on Twitter.

Dennis Jackson, another Echo owner, wrote: "Holy crap, Alexa is down. I can't live. I don't know what to do next. I'm just going to stand still and wait. #scared #alone"

Ashley Mayer, a partner at venture capital firm Social Capital, published a video on Twitter of her asking Alexa for today's news. The light on the top the Echo device lights up but Alexa fails to respond.

Here is a small selection of other tweets relating to the issue:

Monitoring service Downdetector shows that Alexa experienced a sharp increase in "problems" on Wednesday morning.

Business Insider ran its own test at 10:00am (CET) and found no issues with Alexa.

An Amazon spokesperson said in a statement: "This evening [US time] we had an issue that impacted some Alexa customers' ability to interact with the service. The Alexa service is now operating normally."