Olympics Rio 2016: Italian Nibali taken to hospital after crash

Nibali attacked in the closing stages, leading a three-man breakaway on a climb late in the day. He tried to ride away from Colombia's Sergio Henao and Poland's Rafal Majka before he and Henao lost control on a descent so fast that the motorcycle carrying a television cameraman struggled to keep up.

Nibali was attended by medical staff after failing to finish the race, a fate that befell more than half the 144 riders on a crash-heavy day in which many suffered technical problems during an early cobblestoned section of the 237.5km course.

The Italian Olympic team did not immediately respond to a request for comment.

The 31-year-old Nibali has won all three of professional cycling's grand tours - in France, Spain and his native Italy - but has failed to win a medal in three Olympic Games.

Gold medallist Greg Van Avermaet of Belgium said many riders had taken chances.

"Everybody was taking risks and some went over the limit," Van Avermaet told reporters. "A lot of guys wanted to go for it."

Ireland's Dan Martin said the race was one of the toughest he had taken part in.

"It was the most difficult day on the bike I've had in my career," he said after finishing 13th. "It was just a brutal, brutal day."

U.S. rider Brent Bookwalter went even further.

"It was anarchy out there," he said. "Everything happened. People crashing, flatting, getting gapped out in the wind. It was a very hard day."