Air ambulances landed at the scene at Durdle Door on Saturday afternoon, police are now asking people to stay away from the popular tourist spot.
Purbeck Police shared images of the aircraft landing on the sand and crowds leaving the beach as the area was evacuated.
The force warned visitors to expect "high volumes of traffic" as beachgoers left the area having enjoyed Saturday's sunshine.
Purbeck Police said that two helicopters attended the scene for "two separate incidents".
Chief Inspector Claire Phillips, of Dorset Police, said: "We have had to close the beach at Durdle Door to allow air ambulances to land. As a result, we are evacuating the beach and the surrounding cliff area.
"I am urging people to leave the area to enable emergency services to treat the injured people."
Pictures taken earlier on Saturday showed the beach busy as the public were reminded to practise social distancing in the good weather.