ARMED police sealed off a Carmarthen street early yesterday.
Witnesses have described how around 10 marked and unmarked police cars and vans swooped on an address in Belvedere Avenue around 8.20am.
They said around eight officers were carrying guns.
Neighbours claim there had been a party in the house the night before.
"There were police everywhere, I've never seen so many of them," said one resident, who did not want to be named.
"They were telling everyone to get back inside.
"There were eight armed response guys with big guns."
Officers sealed off around 100 metres of road along Belvedere Avenue.
Cars and pedestrians were not allowed to pass.
At around 9.10am police emerged from the property with a man in handcuffs.
The man, from the Swansea area, was put into the back of a van before being taken away.
A spokeswoman for Dyfed-Powys Police said they had received a report of an incident at a property in Belvedere Avenue at approximately 8.10am.
"There were concerns in relation to the behaviour of a man within the property and officers attended the scene with appropriate resources to ensure the safety of the public and officers," she added.
"A 36-year-old man from the Swansea area has been arrested and is currently in custody.
"No-one was seriously injured during the incident."