(Adds comments from French officials)
BOSASSO, Somalia, April 11 (Reuters) - French military helicopters on Friday fired rockets at pirates who had released hostages they had been holding on a captured luxury yacht off the coast of Somalia, witnesses said.
French officials confirmed that troops had fired on a vehicle with pirates on board, but they said they had not shot at people, had not fired any missiles and had not killed anyone.
Local witnesses said an unknown number of people were killed by the rocket fire, which also destroyed three vehicles.
"I could see clouds of smoke as six helicopters were bombing the pirates. The pirates were also firing anti-aircraft machine guns in reaction. I cannot tell the exact casualties," witness Mohamed Ibrahim told Reuters by radio telephone.
The district commissioner of Garaad, where the attack took place, said the helicopters landed and troops jumped out to grab members of a group of 14 pirates who had just come ashore where three pickup trucks with heavy weapons were waiting.
"Local residents came out to the see the helicopters on the ground. The helicopters took off and fired rockets on the vehicles and the residents there, killing five local people," Commissioner Abdiaziz Olu-Yusuf Mohamed told Reuters by phone.
In Paris, French officials said that the operation was conducted with minimal use of force for fear of causing collateral damage.
They said a Gazelle helicopter with a sniper on board and a Panther helicopter with three commandos on board were involved in the incident. In addition two more missile-armed Gazelle helicopters stood by in support but did not intervene.
They said the only shot fired was by the sniper to disable the engine of a vehicle containing the pirates.
"No shots were fired directly at the pirates," Jean-Louis Georgelin, chief of the armed forces general staff, told a news conference.
"The shot from the first Gazelle was enough to stop the vehicle and get out the pirates, who gave themselves up without too much difficulty," he said. (For full Reuters Africa coverage and to have your say on the top issues, visit: africa.reuters.com/) (Reporting by Abdiqani Hassan, additional reporting by Aweys Yusuf and Abdiwahid Sheikh in Mogadishu and James Mackenzie in Paris; Editing by Giles Elgood)