A letter apparently written by suspected gunman Raoul Moat has declared war on the police and promised not to stop "until I'm dead".
The 37-year-old has been on the run since allegedly shooting his ex-girlfriend Samantha Stobbart, 22, and killing her boyfriend, Chris Brown, 29, in Birtley, Gateshead, on Saturday.
A police officer was also shot in his patrol car in Newcastle on Sunday.
Police are dealing with an incident in Rothbury connected to the shootings.
A two-mile exclusion zone has been put in place and people living in the town have been advised to stay indoors.
Earlier officers surrounded a house in the Springwell Road area of Gateshead as part of their operation.
The 49-page handwritten letter allegedly sent to police by Moat, which was also handed to The Sun newspaper, said: "Last night I called 999 and declared war on Northumbria Police before shooting an officer on the West End A69 roundabout in his T5.
"Rang again and told them they're gonna pay for what they've done to me and Sam.
"I went straight but they couldn't let it go.
"The public need not fear me but the police should as I won't stop till I'm dead."
Chip shop robbery
On Thursday Moat was released from prison after serving an 18-week sentence for assault.
Northumbria Police said that on Friday afternoon Durham Prison contacted them to warn them that he had threatened to seriously harm his former girlfriend.
She and her boyfriend were shot in the early hours of Saturday.
The force has referred the matter to the Independent Police Complaints Commission.
Police are trying to trace a black Lexus IS200 SE with number plate V322 HKX which belongs to one of Moat's friends.
They are also investigating an armed robbery at a chip shop in Seaton Delaval on Monday night, about 10 miles from Newcastle, carried out by a man with a similar description to Moat.
Moat is described as white, 6ft 3in (1.90m) tall, with very short or shaven blond hair and a large muscular build.
Police said extra firearms officers from forces including Cleveland, Humberside, West Yorkshire, South Yorkshire and Cumbria, had been brought in overnight to aid in the hunt for Moat.