PLEASE NOTE: EDIT CONTAINS MATERIAL THAT WAS ORIGINALLY 4:3
The emergence of an online video purportedly showing British and Australian Muslims urging people to join the militants fighting in Iraq and Syria has raised fears of spreading extremism.
The men were filmed in Syria in what appeared to be a recruitment video for the Islamic State of Iraq and the Levant militants.
Cressida Dick is a senior British counter-terrorism police officer.
She's warning some foreign extremists now in Iraq or Syra may intend harm closer to home.
(SOUNDBITE)(English) METROPOLITAN POLICE ASSISTANT COMMISSIONER CRESSIDA DICK SAYING:
"They may seek to radicalise others, they may seek to encourage other people to travel, they may seek to incite others to terrorist attacks or violence and of course some of them may perhaps come back here intending to attack people here or in Europe."
Doctor Usama Hasan, a senior researcher in Islamic Studies, says the militants, known