The FBI is probing “unconfirmed information” that a terrorist group was planning to attack next week’s Democratic National Convention.

Media organisations covering the convention would be targeted in the attack, the FBI said.

Officials have said security surrounding the convention, where John Kerry is expected to be nominated as the Democratic presidential candidate, will be on an unprecedented scale.

The FBI has notified all media organisations of the possible terror threat, which they described as “domestic”, but said it would only be releasing more details if there is “any credible information”.