Classified US documents appeared online 4 days ago, including information on Ukraine's air defenses.
US officials have been scrambling to identify the source of the leak and today a 21-year-old air national guardsman, Jack Teixera, has been arrested.
Early reports suggested the source could be an American, in view of the range of documents published.
Jack Teixeira, the man arrested today, was the leader of an online chat group called "Thug Shaker Central". The group's areas of interest include guns, racist memes and video games. Other members of the group have told journalists that the leak was intended to impress group members and was not politically motivated.
Teixera has been arrested by the FBI, "in connection with an investigation into alleged unauthorized removal, retention, and transmission of classified national defense information."
Speaking on his trip to Dublin on Thursday, US President Joe Biden sought to downplay the significance of the leak for US relations.
Sources: PAP, The Guardian, Reuters
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