* French president to fly to Bamako, Timbuktu Saturday
* Amnesty says civilians killed in helicopter strike
* Rights groups allege Malian soldiers killed suspects
By Richard Valdmanis and Benoit Tessier
BAMAKO/TIMBUKTU, Mali, Feb 1 (Reuters) - Human rights groups said on Friday a French-led offensive against Islamists in Mali had led to civilian deaths in airstrikes and ethnic reprisals by Malian troops, a day before President Francois Hollande was due to visit the country.
France has deployed more than 3,500 ground forces in a lightning three-week campaign that has wrested control of northern Mali's towns from an al Qaeda-linked alliance.
The aim is to prevent the Islamist fighters from using Mali's ungoverned desert north to launch attacks in neighbouring African countries and the West.
Residents in the ancient caravan town of Timbuktu have greeted their liberation by French troops with joy, after Islamist radicals had destroyed the town's sacred Sufi mausoleums, burned ancient manuscripts and imposed a harsh form of sharia law, including whippings and amputations.
Amnesty International and Human Rights Watch, however, cited eyewitness reports of extrajudicial killings by Malian government soldiers of dozens of civilians in the central towns of Sevare and Konna.
They said the troops targeted light-skinned Arab and Tuareg ethnic groups associated with the rebels. The Malian military has denied any reprisal killings by its soldiers and the government in Bamako has publicly warned against revenge attacks.
Amnesty also reported that at least five civilians - including a mother and her three children - were killed by a helicopter rocket attack on the morning of Jan. 11 in Konna, seized by the Islamists in an offensive two days earlier.
"Neither the Malians nor the French took the required precautions to avoid hitting civilian targets," Gaetan Mootoo, Amnesty's lead researcher for West Africa, told a news conference in Bamako. "We've asked France and authorities in Bamako to open an independent investigation."
In response, France said it did not begin its military intervention in Mali until the afternoon of Jan. 11 and its helicopters did not target any area inside the town of Konna.
The Malian army has two Hind Mi24 attack helicopters but it is not clear if they are operational.
The allegations of rights abuses came as Paris confirmed Hollande would visit Mali on Saturday, accompanied by Defence Minister Jean-Yves Le Drian and Foreign Minister Laurent Fabius.
Hollande would meet Mali's Interim President Dioncounda Traore in the southern, riverside capital Bamako before travelling up to Timbuktu to greet French troops, an Elysee diplomatic source told Reuters.
"The president will visit Mali to express his support and gratitude to French troops fighting at the request of Malian authorities and the international community against the terrorist groups which invaded Mali's north," the source said.
U.S.-based Human Rights Watch cited evidence that Malian soldiers executed at least 13 people suspected of collaborating with the Islamist rebels and forcibly 'disappeared' five others in Konna and the garrison town of Sevare, also in central Mali.
"Malian authorities have turned a blind eye to these very disturbing crimes," said Corinne Dufka, senior West Africa researcher at Human Rights Watch. "The Malian government should take immediate steps to investigate these abuses and bring those responsible to justice, irrespective of rank."
Witnesses in Sevare described how Malian soldiers arrested and executed the men and dumped their bodies in a public well in broad daylight after they failed to producer proper identification at a bus station. Residents in Sevare had given a similar account of the killings to Reuters.
HRW also documented the execution of at least seven Malian soldiers, five of them wounded, by Islamists during their capture of Konna.
Both rights organisations said the Islamists had recruited child soldiers, sometimes offering large sums of money to their parents or to the teachers of Koranic schools. One of the boys told Amnesty that the rebels injected child soldiers with a substance before combat to give them courage.
France is now due to gradually transfer the military mission in Mali to a U.N.-backed African force of some 8,000 soldiers, tasked with securing northern towns and pursuing militants into their mountain redoubts near Algeria's border.
French air strikes have destroyed the Islamists' training camps and logistics bases but Paris says a long-term solution hinges on finding a political settlement between Mali's restive northern Tuareg community and the distant capital Bamako.
Under pressure from Paris, Traore has said he is ready to open talks with the Tuareg rebel MNLA group provided it drops its demands for independence for northern Mali.
Dialogue with the Tuaregs could anger Mali's powerful military, which toppled the civilian government in March last year in frustration at its handling of the Tuareg uprising.
It is still angry over the execution of some 80 soldiers by Islamists at the northern town of Alguelhoc. The soldiers, who ran out of ammunition, were shot dead or had their throats slit.
"We agree to negotiate but not with people who have committed crimes," said one senior Malian military source. (Reporting By Richard Valdmanis, David Lewis and Tiemoko Diallo, Jean-Baptiste Vey and Julien Ponthus in Paris; Writing by Daniel Flynn; Editing by Pascal Fletcher and Jon Boyle)