By Richard Valdmanis and Benoit Tessier

BAMAKO/TIMBUKTU, Mali (Reuters) - A French-led offensive against Islamists in Mali has led to civilian deaths from air strikes and ethnic reprisals by Malian troops, human rights groups said on Friday, a day before President Francois Hollande was due to visit the country.

Amnesty International and Human Rights Watch cited witness reports of extrajudicial killings by Malian government soldiers of dozens of civilians in the towns of Sevare and Konna. At least five civilians were killed in a helicopter attack on the first day of France's military intervention, Amnesty also said.

France has deployed more than 3,500 soldiers in a three-week campaign that has wrested control of northern Mali towns from the al Qaeda-linked rebels and aims to prevent Islamist fighters from using Mali's desert north to launch attacks on African countries and the West.

"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."

The human rights groups said troops targeted light-skinned Arab and Tuareg ethnic groups associated with the rebels. The Malian army has denied any summary executions by its soldiers and the government in Bamako has publicly warned against such revenge killings.

In its report, Amnesty said a mother and her three children were among the five civilians killed in a helicopter rocket attack on the morning of January 11 in Konna, seized by the Islamists in an offensive two days earlier.

In response, France said it did not begin its military intervention in Mali until the afternoon of January 11 and its helicopters did not target any area inside the town of Konna.

"Everything is done in the planning to avoid collateral damage on the civilian population," said Foreign Ministry spokesman Philippe Lalliot. He said French air attacks were precisely targeted to avoid civilian deaths.

A Malian military source in Bamako, asking not to be named, said its forces carried out strikes in Konna before the French intervened. Mali's army has two Hind Mi24 attack helicopters.

The allegations came as Hollande announced he would visit Mali on Saturday to meet interim President Dioncounda Traore in the southern riverside capital Bamako and greet French troops in Timbuktu.

"I am going to Mali tomorrow to express to our soldiers our support, our encouragement and our pride," Hollande said during a visit to the Val d'Oise. "I am going to Mali tomorrow so that African troops come as quickly as possible join us."

France is 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.

Hollande, who repeated calls for talks in Mali to heal the deep political rift between north and south, said he would comment on speculation France might quickly reduce its troop deployment in Mali after liberating the main towns.

In the ancient caravan town of Timbuktu, residents greeted their liberation by French troops with joy this week, 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.

"BLIND EYE" Continued...