One of the men seen outside the UK school attended by the children is understood to be an international press photographer.
He made the call almost an hour before a farmer also called police after seeing men in balaclavas.
In a television interview the US Secretary of State mentioned Iran, which has denied any involvement
BBC correspondent Daniel Sandford explains where the investigation goes from here.
The firm also issued an update on incidents in which its models accessed Australian government systems.
Five men have been arrested on suspicion of explosive and terrorism offences after a major incident was declared at an airbase in the west of England.
The US-Israel war with Iran has caused fuel prices to soar.
Illegal registration plates are far too easy to get hold of and are putting the public at risk, BBC is told.
The prime minister told the BBC that social care in England is "as unfair as American healthcare".
East Suffolk and North Essex NHS Foundation Trust says it has launched an "urgent" investigation.
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