Image copyright Ramsey County Sheriff's Office

The son of former US Democratic vice-presidential nominee Tim Kaine has been arrested in a protest against a pro-Donald Trump rally in Minnesota.

Linwood Kaine, 24, was among five people detained on Saturday in a clash with Trump supporters outside the Minnesota State Capitol in St Paul.

He was accused of second-degree rioting, but was not charged.

His father, Tim Kaine, who was Hillary Clinton's running mate, expressed disapproval.

Image copyright AFP

The Virginia senator said in a statement released to the Pioneer Press through a spokesperson: "We love that our three children have their own views and concerns about current political issues.

"They fully understand the responsibility to express those concerns peacefully."

The youngest son of Senator Kaine was released from jail on Tuesday morning.

He was among a group that disrupted the rally in support of the president with a smoke bomb, air horns and chants, reports the Pioneer Press.

A 61-year-old woman was reportedly struck in the head in the fracas, according to the newspaper.

The Ramsey County Attorney's Office said neither Linwood Kaine nor the other demonstrators would be prosecuted due to "insufficient facts to prove felony-level riot".