The twin teenage girls who are thought to have travelled to Syria are "clearly posing a threat to themselves and potentially the community," police investigating their disappearance said.
Detective Chief Superintendent Tony Mole, head of the North West Counter Terrorism Unit which is leading the investigation, said: "First, I want to stress that the welfare of these two teenagers is our overarching priority."
He added: "Two 16-year-old girls left the UK on 26 June 2014 and we believe that they have since entered Syria."
At this stage he said police don't know the location of the girls, whom ITV News understands are called Salma and Zahra Halane. Officers were trying to establish who they are with.