Armed police swooped on a street in Wigan as they made the fifth arrest in the investigation into the Manchester bombing.
The town centre was in lockdown as officers carrying automatic weapons carried out the raid.
Witnesses say a man was tackled to the ground in Upper Dicconson Street after he was seen with a suspicious package.
Photos shared on social media appear to show him being led away by plain clothes officers with their faces covered wearing black police caps.
Wigan Council warned people to avoid the area because of an “ongoing police incident”.
A nearby nursery, Little Acorns, was put into lockdown and warned parents not to come to collect their children.
“We are currently on lock down due to an incident in the area,” a statement on its Facebook page said.
“We are safe. All children are upstairs. Please DO NOT come for your children at little Acorns you will not get in.”