A US army veteran has been arrested in southern California after discussing plans to carry out terror attacks on both Jews and Nazis.

Mark Domingo, 26, discussed carrying out attacks on both a White Supremacist rally and Jews walking to synagogue as a way of avenging last month’s far-right terror attack on mosques in Christchurch, New Zealand.

A recent convert to Islam, Mr Domingo said he desired “martyrdom” and to bomb Santa Monica pier during the summer in order to maximise casualties and give America “a taste of the terror they gladly spread all over the world.”

At a press conference on Monday, US Attorney Nick Hanna said Mr Domingo was “consumed with hate and bent on mass murder.”

Mr Hanna described how, as well as planning to target a white supremacist rally at Bluff Park, Long Beach on Sunday, the suspect also “said he wanted to kill Jews as they walked to synagogue. At other times he said he wanted to target and kill police officers.”

The 26-year old, who previously served a tour in Afghanistan, had been under 24 hour surveillance after being identified online by the FBI.

He was arrested in an sting operation after he purchased pressure cookers and more than 3.5 kilograms of nails, providing them to a man posing as a bomb maker who was actually an undercover agent.

Had Mr Domingo in fact managed to carry out a bombing at the park in Long Beach on Sunday, he would not have killed any Nazis: despite an announcement of plans for a White Supremacist gathering in the park, none had showed up.

However, the bomb could have ended up killing anti-fascist counter-protestors, a large number of which did assemble in the area.

“Sometimes we get asked ‘what keeps you up at night?’ This is a case that keeps us up at night,” Ryan Young, an FBI agent, told the press conference.

The arrest on Friday came 24 hours before a separate attack on a synagogue in southern California, killing one congregant and injuring others, including the rabbi.