Neighbours said they were told to "stay inside for their own safety" when masked armed police officers descended on a north Liverpool street.
Eyewitnesses said a huge police operation involving armed officers and police dog units "came out of nowhere" on what is normally a "quiet" stretch of the East Lancs Road.
The operation forced them to take refuge in their homes while the road between Stopgate Lane and Scargreen Avenue was closed for much of Sunday afternoon.
Residents told the ECHO a group of about 20 armed police wearing masks and carrying "massive" guns swooped on the road before going inside a house.
One witness who the ECHO spoke to at the scene said they were "rushed inside" by police.
She added: "It was about 2.30 or 2.45pm, there must have been about eight vehicles and 20 or so officers. They had massive guns.
"It's usually a quiet road here so it was quite scary. No one really knows what's going on."
Other neighbours said they were rushed inside and advised to stay inside for their safety by armed officers while the operation got underway.
Merseyside Police were contacted for comment but could only confirm they were at an "ongoing police incident."
The operation appeared to focus on one residential property which witnesses said was the subject of a search involving dog units and police officers on Friday evening as well.
Armed officers and police dogs units were pictured surrounding the property before going inside.
The property was surrounded by Matrix vans and police cars for several hours, though the road closure was reduced during that period.
During that time officers could been seen going to and from the property and carrying equipment, with some stationed outside appearing to guard the property.
They were also seen searching the front garden, including looking in the wheelie bins.
Police could be seen leaving with an evidence bag just before 5pm.
