A 24-year-old man has been arrested in connection with the 2017 Manchester Arena terror attack.
He was detained shortly after arriving back in the UK, police said.
He was arrested on suspicion of assisting or engaging in the preparation of acts of terrorism/assisting others in acts of preparation under section 5 of the Terrorism Act (2006).
On Friday evening, the man remains in custody for questioning.
The senior investigating officer for the investigation, Simon Barraclough, said: “Greater Manchester Police remains firmly committed to establishing the truth surrounding the circumstances of the terror attack at the Manchester Arena - whether that is by supporting the on-going public inquiry or by continuing to pursue leads with regards to the criminal investigation.
“Over four years have passed since the atrocity took place but we are unwavering in our dedication to follow each line of enquiry available so that we can provide all those affected by the events at the arena with the answers they rightly deserve.”
It is understood that the man is not Ismail Abedi, the brother of bomber Salman Abedi, who fled the UK ahead of an appearance at the arena bombing inquiry.
The terror attack took place shortly after an Ariana Grande concert at Manchester Arena on 22 May, 2017. Twenty-two people died.