Image copyright EPA Image caption Black performed with his band Tenacious D in Germany on Friday and Saturday

Online speculation that US actor Jack Black had died was the work of a hacker who posted messages on his rock band's official Twitter account.

Fans expressed dismay after a message on Tenacious D's Twitter page claimed Black had died at the age of 46.

Subsequent messages, however, appeared to suggest the group's account had been hacked.

This was later confirmed by Tenacious D themselves, who called the hacking a "sick 'prank'".

"WE had our Twitter account hacked," the band tweeted on Sunday afternoon. "We can assure you that Jack is ALIVE and WELL."

John Konesky, a guitar player with Tenacious D, also confirmed the tweets were the result of hacking.

Image copyright @RealTenaciousD/Twitter

Neither Black not his band's US and UK representatives have made a statement, but fans had been quick to rubbish the alleged claims.

One Twitter user said Black was on a plane headed to Los Angeles following his appearance with bandmate Kyle Gass at two music festivals in Germany.

It is not the first time Black, whose films include the Kung Fu Panda trilogy and School of Rock, has been the victim of an online hoax.

One in 2012 claimed he had fallen off a cliff in New Zealand, while another in 2014 alleged he had died after a stroke.