"Counter Terrorism Policing South East (CTPSE)... have recovered evidence that indicates the attack at an immigration centre in Dover on Sunday, 30 October 2022, was motivated by a terrorist ideology," the body said in a statement.
The evidence recovered -- including from devices -- suggested "there was an extreme right-wing motivation behind the attack," it added.
Tim Jacques, senior national coordinator for Counter Terrorism Policing, added that while there were "strong indications that mental health was likely a factor", he had concluded that the "suspect's actions were primarily driven by an extremist ideology".
These met the "threshold for a terrorist incident", he said.
Homemade incendiary devices were thrown at the Western Jet Foil Border Force centre in Dover on Sunday, leaving two staff with minor injuries.
The facility in the busy port town in southeast England processes migrants who have crossed the Channel from northern Europe in small boats.
The attack was carried was out by a 66-year-old man who was later found dead.
"There is currently nothing to suggest the offender was working alongside anyone else and there is not believed to be any wider threat to the public," the statement said.
The British government is currently grappling with how to deal with a record number of migrants crossing the Channel from northern Europe in small boats.
Since the beginning of the year, an unprecedented 38,000 people have made the perilous journey, the government's home affairs select committee was told on October 26.
Britain's Home Secretary Suella Braverman earlier this week caused outrage -- and earned a rebuke from the new UN rights chief -- for describing the arrivals as an "invasion".
This story has been published from a wire agency feed without modifications to the text.
