Microblogging site Twitter is suspending accounts of users who tweet images or videos of  what is said to be the beheading of U.S. photojournalist James Foley.

Twitter CEO Dick Costolo announced the decision in his own twitter account, Wednesday, The Telegraph in Britain reports.

After sharing a link to a news story about Foley's alleged killing, Costolo wrote, 'We have been and are actively suspending accounts as we discover them related to this graphic imagery. Thank you."

The five-minute video shows a masked man standing next to Foley. After his anti-American statements, the man beheaded the journalist. The executioner claims to be part of extremist Islamist Islamic State movement.

The man says, "This is James Wright Foley, an American citizen, of your country. As a government, you have been at the forefront of the aggression towards the Islamic State."

Foley had previously been captured and imprisoned while working in Libya, the British site Christian Today wrote.

Talking of his mother's strong faith and the prayers of his friends and family at this time, Foley wrote to his alumni magazine.

"It felt energizing to speak our weaknesses and hopes together, as if in a conversation with God, rather than silently and alone," Christian Today reported.

"If nothing else, prayer was the glue that enabled my freedom, an inner freedom first and later the miracle of being released during a war in which the regime had no real incentive to free us. It didn't make sense, but faith did."

This week Foley's mother Diane wrote a moving tribute to her son on a Facebook page campaigning for his release. "We have never been prouder of our son Jim," it said. "He gave his life trying to expose the world to the suffering of the Syrian people."

Zaid Benjamin, radio correspondent in Lebanon, was among the first to tweet about the video.

Twitter temporarily suspended the account after deleting the tweet containing the video. Twitter said in a message to Benjamin that his account was suspended because he violated Twitter rules.

Costolo's message follows other Twitter users rallying others not to retweet the video titled, "A Message To America."

Thousands of ordinary users from around the globe supported the move not to share the beheading footage using the hashtag #ISISmediablackout.

Besides the Foley beheading, the IS video also contained the message that another American journalist, Time magazine contributor Steven Sotloff will be killed unless the United States stops airstrikes in Iraq. Sotloff went missing in northern Syria in July 2013.

A U.S. official told the Associated Press that the video appears authentic.

Two other U.S. officials said the victim was Foley and his family has confirmed he is the man executed in the video.

Both Twitter and YouTube have reportedly moved to ban graphic images of the Foley video.