Two French soldiers and a French hostage have been killed during a failed operation to free him in Somalia, the defence ministry says.Commandos backed by helicopters reportedly swooped on the southern town of Bulo Marer during the night, targeting al-Shabab militants.According to the defence ministry, the hostage was killed by his captors.The raid in east Africa came hours after French troops intervened in the west African state of Mali.The French military is believed to have been trying to free a French secret agent named as Denis Allex, who was kidnapped in Somalia in July 2009 along with a colleague, freed the following month.It seems likely that the operation was linked to the intervention in Mali, the BBC’s Hugh Schofield reports from Paris. The French government knew well the intervention would have dangerous implications for the nine French hostages being held across northern Africa, our correspondent says.Bodies Eyewitnesses in the town in the lower Shabelle region heard fighting during the night, then saw bodies on Saturday.Up to four helicopters were involved in the operation, they said.Mohamed Ali, a resident of Bulo Marer, told AP news agency by phone: "We heard a series of explosions followed by gunfire just seconds after a helicopter flew over the town."We don’t know exactly what happened but the place was an al-Shabab base and checkpoint.”Another resident of the town, Idris Youssouf, told AFP that details were sketchy because the attack had happened at night."But this morning (yesterday) we saw several corpses including that of a white man,” he added. He said three civilians had also died in the fighting.According to the French defence ministry, 17 militants were killed in the fighting.Hostage appeal Of the other French hostages, at least six are being held by the al-Qaeda in the Islamic Maghreb group, AFP reportsMr Allex, reportedly an agent of France’s DGSE intelligence service, appeared in a video in June 2010, appealing to France to drop its support for the Somali government.He last appeared in another video in October, looking gaunt and calling on French President Francois Hollande to work for his release.Somalia has not had an effective central government for more than two decades.France has a large military base in neighbouring Djibouti, including army, marine and air force units. Agencies