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."
Greater Manchester Police said: "We have made an arrest in Wigan this afternoon in connection with the investigation into the horrific incident at Manchester Arena.
"The man was carrying a package which we are currently assessing, a police cordon remains in place while this is carried out."
An officer in a white forensic suit is examining a red bag which the suspect was carrying, according to one witness, who did not want to be named.
"There was a lot of officers coming in with a few cars from different directions," the restaurant owner said.
"They wrestled with a man on the floor and he had a red bag.
"Now there's a man in a white suit looking in the bag – he's taking something out of it.
"They've sealed the whole area off, put tape around the perimeter.
"My restaurant is in the middle of it and I can't open my front door.
"There were a lot of armed officers with their faces covered - with balaclavas and machine guns.
"They told us to get in, lock the windows and close the doors."
He said he has not seen the arrested man before.
"We've never had something like this happen here before. Hopefully it's a one-off," he said.
