Ten civilians including three children have been killed in fighting in the central Mali city of Konna between the Malian army backed by French forces and Islamist rebels, Human Rights Watch said Saturday, citing area residents.

"Konna residents told Human Rights Watch some 10 civilians were killed in the fighting including three children who drowned trying to cross the river to safety," said the rights group's Corinne Dufka in a message sent to AFP in Dakar.

She also raised concerns about children who she said have been recruited by the Islamists as soldiers.

"Other children recruited by the Islamists in Gao have been wounded and possibly died in the fighting," she said, referring to a city in north Mali under the control of the radical Islamists, some of whom are linked to Al-Qaeda in the Islamic Maghreb (AQIM).

Dufka, a senior researcher at Human Rights Watch, said that in the past few months children from Mali and also neighbouring Niger have been taken by the Islamists, and "must be immediately released."

"Furthermore, the Islamists' threats to retaliate against French non-combatants, including hostages, are totally reprehensible and would constitute war crimes. All parties involved in this conflict -- Islamist groups, Malian and French army, and (regional) troops -- should do all they can to protect civilians and strictly adhere to the law of war," she said.

Mali's army took back the key town of Konna from Islamist rebels on Saturday aided by French air power, with Burkina Faso, Niger and Senegal each pledging 500 troops to an African force tasked with regaining the north of the country now controlled by the Islamists.

The battle left dozens of dead rebels strewn across the area, according to witnesses and the Malian military. The French military suffered one casualty, a pilot killed carrying out air raids, said French Defence Minister Jean-Yves Le Drian.