Thomson Reuters has dismissed Matthew Keys, the deputy social media editor of Reuters.com who was indicted on charges of aiding members of the Anonymous hacking collective, Keys said in a Twitter message on Monday.

Thomson Reuters spokesman David Girardin said that Keys was no longer with the company, effective Monday, and declined further comment.

Keys was indicted in March by a federal grand jury in Sacramento, Calif., on three criminal counts alleging that he helped members of the Anonymous collective hack into computer systems of the Tribune Co. The alleged events occurred before he joined Reuters, the indictment indicated. He has maintained his innocence, and his arraignment is scheduled for Tuesday.

In his job at Reuters, Keys posted news from Reuters and other sources on both company Twitter feeds and other means, including his own Twitter account. He was suspended from Reuters after last month's indictment and his access to his Reuters email account was cut off. He continued to tweet from a personal account, @TheMatthewKeys, and identified himself as an editor at Reuters.

Keys in a blog post on Monday wrote that his coverage of the Boston Marathon bombing last week - such as tweeting information from police scanners that ended up being incorrect - was one of the reasons he was given for his termination.

Keys also posted a copy of what he said was a warning from the company in 2012. That document cited a parody Twitter account he created in 2012 in which he lampooned Google CEO Larry Page after the company prematurely released its quarterly results. Keys revealed himself as the author a few days after the account's creation.

Keys maintains his dismissal was groundless and said he would contest it with help from the union that represents Reuters journalists, the Newspaper Guild of New York. Deborah Zabarenko, the unit chair of the union at Reuters, said in an email that the Guild "does plan to grieve this and arbitrate it if necessary."