Florida man attacked by alligator after falling off bike

A man was seriously injured in the US state of Florida after falling off his bike and into a body of water, where he was attacked by an alligator, according to police.

The man was riding his bike on a trail at Halpatiokee Park in Stuart, some 160 kilometres north of Miami, around 11 am (1500 GMT) Monday, when he lost control and fell into a body of water about two metres down an embankment, Martin County Sheriff's Office said in a statement.

Police said the man was attacked by a female alligator about 2.7 metres long but, despite being severely injured he "was able to break free then crawl to an area where he was assisted by a bystander."

Emergency services gave the man first aid and drove him away from the park, where he was loaded on a Martin County Fire Rescue helicopter.

A trapper was later able to capture the animal, the sheriff's office said, adding that Florida Fish and Wildlife officers were in charge of the investigation.

A witness told broadcaster WPTV that the man "had a lot of marks all over his leg, but mainly in the upper thigh."

"He was hanging on roots like five feet below," the witness said. "It was hard to get him out."

The witness, who was walking his dog when he spotted the cyclist, said he used his dog leash as a makeshift tourniquet as he and other bystanders lifted him out of the water.

Alligators are particularly aggressive at this time of the year.

However, serious injuries caused by alligators are rare, according to the Florida Fish and Wildlife Conservation Commission.