A US journalist charged with conspiring with the hacker group Anonymous to break into and alter an online Los Angeles Times story said Monday he has been fired by Reuters.

Matthew Keys, 26, sent out word via Twitter that the news agency had dismissed him.

"Just got off the phone. Reuters has fired me, effective today," Keys said in the message. "Our union will be filing a grievance. More soon."

A spokesman for Reuters' parent firm, Thomson Reuters, confirmed that Keys was "no longer with the company" but declined further comment.

The Justice Department announced last month that Keys was indicted in California on three criminal counts related to hacking allegedly carried out before starting at Reuters.

He faces up to 10 years in prison and a $250,000 fine.

According to a federal grand jury indictment in Sacramento, Keys provided Anonymous members with login credentials to a computer server belonging to the Tribune Co., which owns the Times, in December 2010.

He had been fired from his post as a Web producer at a Tribune-owned television station in Sacramento -- KTXL FOX 40 -- two months earlier.

A hacker used the credentials provided by Keys to log into the Tribune server, and ultimately made changes to the online version of a Los Angeles Times news story, according to prosecutors.

Keys joined Reuters in 2012, more than a year after the alleged crimes.