Police officers in a town in the northwest of the United States have received death threats after the arrest of 31 far-right activists accused of planning to carry out violence at a Pride party, it has been reported the local police chief on Monday.

The activists, linked according to the police to the nationalist group "Patriot Front", were intercepted on Saturday in Coeur d'Alene, Idaho, after a call from a local resident reporting "what looked like a small army" of masked men piled into a truck.

They were equipped with "shields, shin guards and other riot gear ... including at least one smoke grenade," according to police chief Lee White.

They were charged with attempting to organize violence.

Lee White said his office had received about 150 calls from anonymous callers since Saturday. “They shouted and yelled at us” and “made death threats against myself and other police officers, for simply doing our job,” he explained during a press conference.

He blamed the threats on "hate groups outside" the city, with one of the calls even coming from Norway.

The police officer said he was surprised at the “degree of preparation” and “equipment” of the militants.

“It was immediately very clear that it was a group of rioters” with “malicious intentions”, he added.

The men arrested come from at least 11 American states, he said, indicating that he had never had any dealings with the "Patriot Front" group in Idaho.

This mountainous region of northwestern Idaho has long been associated with the neo-Nazi group “Aryan Nations,” which hoped to found a territory there exclusively populated by white people and committed numerous violent crimes throughout the country.

But Coeur d'Alene Mayor Jim Hammond assured the area was not going to "go back to the days of the Aryan Nations" and was "able to get rid of this group and the horrible culture" that he was trying to promote.