Officers said Battle Road, in St Leonards, has been closed at the junction with Upper Glen Road after a man armed with a knife locked himself in his property.
East Sussex Fire and Rescue Service were called at about 9.40am to reports of a fire at the home.
Police said the man refused to let firefighters in and is still inside the property.
A police spokesman said: “Emergency services are currently dealing with a man who is armed with a knife and refusing to leave his property in Battle Road, St Leonards.
“East Sussex Fire and Rescue Service was called to the address at 9.37am on Sunday (November 19) following a report of a fire. The occupant refused to let firefighters in and is still inside the property.
“Police are attempting to negotiate with the man and part of Battle Road, with the junction of Upper Glen Road, is closed.
“The fire is out and the incident is ongoing.”
No-one else is believed to be in the property.
Officers added the incident is not connected with last night’s stabbing in Battle Road.
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