Steve Bannon has been arrested after allegations of fraud relating to an online fundraising scheme, the US Justice Department said on Thursday.

US President Donald Trump's ex-political adviser was detained on charges of conspiracy to commit wire fraud as part of a project to raise money to support the building of a wall along the United States' border with Mexico.

The charges in detail

Bannon and three of his associates — Brian Kolfage, Andrew Badolato, and Timothy Shea — were indicted by investigators in New York after federal prosecutors alleged that the scheme garnered "more than $25 million (€21 million) to build a wall along the southern border of the United States."

The project "orchestrated a scheme to defraud hundreds of thousands of donors," the prosecutors added.

The indictment alleges Bannon pocketed over $1 million, despite promising donors that 100% of the money raised would be used to fund the construction of Trump's much-vaunted plan.

Kolfage, who founded the project, siphoned $350,000, according to the indictment.

The "We Build The Wall" website claims it will bring people "together to build segments" of the barricade and will do so at "a fraction of what it costs the government." The project also states in is a "non-profit tax-exempt organization."

Bannon's influence

Bannon served as Chief Strategist in the White House during the first seven months of Trump's term.

Prior to joining Trump on his presidential campaign as it entered its final few months, Bannon was the executive chairman of the online media outlet Breitbart News. The 66-year-old has relinquished his roles at Breitbart and the data-analytics firm Cambridge Analytica, where he served on the board.

Trump 'feels bad'

President Trump said he felt "very badly" about the arrest of Bannon but knows nothing about the fundraising organization involved in the federal criminal case.

"I do think it's a sad event," Trump told reporters in the Oval Office. "I haven't dealt with him at all now for years, literally years."

Last month, Trump was keen to distance himself from the scheme. He tweeted: "I disagreed with doing this very small (tiny) section of wall, in a tricky area, by a private group which raised money by ads. It was only done to make me look bad, and perhaps it now doesn't even work."

jsi/rt (AP, Reuters, dpa)