American cycling legend Lance Armstrong suffered a broken collarbone during an event in Spain on Monday, an injury that threatens to disrupt his bid to win a record eighth Tour de France title this summer.
The 37-year-old fell along with several other riders about 20 kilometres (32 miles) from the finish line of the first stage of the Tour of Castilla y Leon in central Spain.
He was then seen clutching his arm sitting on the grass after taking his helmet off.
"Lance Armstrong suffered a break in the middle of his right collarbone," the race organisers said in a statement after the rider underwent an X-ray at a hospital in the city of Valladolid.
"After receiving medical attention and treatment for pain, Armstrong left the hospital this afternoon."
The rider said he was devastated over the accident."
It has never happened before, I feel very disappointed," he told reporters as he left the hospital. "I feel miserable right now so I have to relax a few days."
He nodded his head when asked if he would return to the United States.
Armstrong, a cancer survivor who went on to claim a record seven Tour de France crowns, ended a three-and-a-half year retirement at the Tour Down Under in Australia in January.
He declared his goal this year is to win an eighth Tour de France title in July, and had hoped to use the Castilla y Leon race as part of his preparations.
Armstrong told reporters his participation in the Giro d'Italia in May "will be very complicated", an indication that he still hopes to compete in the Tour de France two months later.
The manager of his Astana team, Johan Bruyneel, said the injury was "a clean fracture without complications" and he should make a "fast recovery."
In his last outing on Saturday, Armstrong finished in 125th place in the Milan-San Remo in Italy, his first European race since July 2005.
His return to the sport has sparked rumours of friction between him and teammate Alberto Contador of Spain over who will be chosen to lead the Astana's team's challenge in the Tour de France.
The Tour of Castilla y Leon was the first time the two have raced alongside each other with Astana. Contador, the 2007 Tour de France champion, won the last two editions of the event.
"It was a shame to lose Lance," Contador said. "We could see that he wanted to use this race as part of his preparations. It was a good chance for us to work together."
Armstrong has also been dogged by unproven doping allegations in his career.
Last week, he said he was subjected to his 24th anti-doping control since August 2008, a month before he officially announced his comeback to professional road cycling.
Following Armstrong's accident, the first stage of Castilla y Leon race was won by Spain's Joaquin Sobrino ahead of Switzerland's David Vitoria.
Sobrino covered the 176.3 kilometres between Paredes de Nava and Baltanas in 4 hours, 31 minutes, 12 seconds.
Results of first stage of the Tour of Castille and Leon cycling race here on Monday, a 176.3 kilometres ride from Paredes de Nava:
Stage and overall
1. Joaquin Sobrino (ESP) Burgos Monumental 4hr 31min 53sec, 2. David Vitoria (SUI), 3. Jose Joaquin Rojas (ESP), 4. Ruben Perez (ESP), 5. Manuel Cardoso (ESP) all same time