Detective chief supt Tony Mole, head of the force’s North West Counter-Terrorism Unit, said: “First and foremost I should reassure everyone that none of today’s activity is linked in any way to any imminent threats in Greater Manchester or the UK.
“The operation has been running since autumn 2013 since we first became aware of a number of individuals travelling from the North West to the battlefields of Syria.
“You may have seen headlines in recent months linking people from Manchester to Syria and you will naturally have been concerned about this.
“Like other major cities across the UK we have been aware for some time of people travelling to war-torn places for terrorism-related purposes. This is not a problem unique to Manchester or the North West - it is an issue that affects different communities across the country and elsewhere.”
Mr Mole said travelling to a war zone in order to be involved in conflict - or supporting those who do so - could make them potentially liable to prosecution for terrorism offences.
He said: “As well as posing a risk to themselves, there is the very real threat that they could pose a danger to our own communities when they return to the UK.
“There is naturally widespread concern about the situation in Syria and other conflict zones and the way that some will be driven to travel there to engage in humanitarian work or to take part in the fighting. We know that some have already lost their lives or been detained by the regime and badly treated.
“There are serious concerns that anyone travelling to Syria, whether for humanitarian reasons or because of a desire to support the Syrian opposition, may be targeted by extremist groups who want to recruit them. This could have serious repercussions for the safety of the individual concerned.
“By travelling there people will be causing distress and anxiety to their families and friends, not to mention the wider community.”
Anyone wanting to report suspected terror-related activity can call the Anti-Terrorist Hotline on 0800 789 321.