Fan remains in hospital after Tour Down Under crash

A fan remains hospitalised with serious injuries after Saturday's Tour Down Under cycling crash.

Video on social media taken by another spectator shows four cyclists hitting the barricades at high speed on the last corner of the street circuit race.

One rider went over the top of the barrier and into the crowd.

On Sunday morning, SA Premier Peter Malinauskas called it an "awful, freak accident".

"Tragically last night we did see a significant accident occur at the TDU, where cyclists went into spectators," the premier said.

"It's saddening to report a woman has suffered multiple serious injuries."

He added the woman was visiting from NSW with her husband.

A race statement said organisers are in contact with the spectator's family and are offering support.

The lead riders in the one-hour street race rounded the final bend without incident, but four others cannoned into the barricades.

One race official said riders had taken the final corner 20km/h quicker, compared to previous laps.

The Adelaide parklands circuit was the same one that was used to launch the first Tour Down Under in 1999.

But the debut race went counter-clockwise, not clockwise, and that meant a much less sharp corner into the final straight.

Italian rider Manilo Moro (Movistar) was the only one of the crashed riders who was unable to finish the race.

He needed help from a team staff member as he slowly rode to the finish, looking the worse for wear.

It is understood Moro is undergoing more treatment.

The classic, a one-off race, is a fixture of the Tour Down Under. It lets overseas riders have a hitout at the start of the season before the Tour itself.

The six-stage Tour, celebrating its 25th anniversary, starts on Tuesday.

Australian Sam Welsford (Red Bull Bora Hansgrohe) won Saturday's race.