Four people have been arrested by police on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism in Syria
Two men aged 29 and 18 both from Levenshulme, and a 21-year-old woman from Trafford are in custody, Greater Manchester Police said.
A 29-year-old man from Oxford has been arrested by the South East Counter Terrorism Unit on suspicion of the same offence.
Police said a number of properties were now being searched as part of the investigation.
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The ashes of backpacker Mia Ayliffe-Chung who was stabbed to death in Australia will be scattered around the world, her mother has said.
Around 60 people were also injured in the attack in the port city of Aden.
The British Medical Association also called for doctors to have no more than 25 consultations a day to reduce the burden placed on them.