* MNLA offers to join international mission
* Warn of reprisals against Tuaregs by Malian army
* Rights groups cite reports of killings by security forces
By Nathalie Prevost
NIAMEY, Jan 20 (Reuters) - Mali's MNLA Tuareg separatists said on Sunday they were ready to join international efforts to liberate northern Mali from Islamist rebels, amid fears the Malian army could exact revenge on Tuaregs for an uprising last year.
The MNLA launched a rebellion in northern Mali early in 2012, wresting control of the region from government forces after a military coup in March which was prompted by the government's handling of the uprising.
The Tuareg uprising was quickly hijacked by an alliance of Islamist groups, which had initially fought alongside them but soon drove them from power in the main cities of the desert region the size of Texas, dubbed Azawad by the rebels.
With France's dramatic military intervention 10 days ago having reversed an Islamist advance southward, MNLA spokesman Ibrahim Ag Mohamed Assaleh said the movement's dispersed fighters could be recalled to support a U.N.-mandated intervention by forces from West African regional bloc ECOWAS.
"The MNLA wants to fight the terrorists, alongside ECOWAS and the international community," he told Reuters television in an interview in Niamey, the capital of neighbouring Niger.
With many in Mali's capital Bamako furious at the Tuareg for their role in the current crisis, the country's powerful military is unlikely to sanction them taking any official role in an operation to liberate the north.
While some Tuaregs support the Islamists, particularly in the Ansar Dine faction founded by former separatist leader Iyad ag Ghali, many of them do not and resent its fundamentalist form of Islam at odds with the region's traditionally moderate Sufi beliefs.
"The population of Azawad, for whom we are fighting, are the first victims of this terrorism and we are afraid they will also become victims of the military operation, especially from the Malian army," Assaleh told Reuters.
The United Nations refugee agency UNHCR said last week that Malians fleeing to neighbouring countries had related "horrific accounts" of human rights abuses under the Islamists, including rape and executions of opponents, plus amputations and stoning to death under an extreme version of sharia law.
The International Criminal Court has launched an investigation into suspected war crimes in Mali.
Meanwhile, there is growing concern of ethnic cleansing as Mali's army retakes the north with French assistance.
Human Rights Watch (HRW) said on Saturday it had received credible reports of serious abuses, including killings, being committed by Malian security forces against civilians around the central town of Niono. Malian army officials have strongly denied this.
"Anyone can get a Malian army uniform and do whatever they like. It has been known to happen," said Colonel Seydou Sogoba, in charge of Malian army operations in the area. "Even the jihadists have done this sometimes to discredit the Malian army."
HRW said that Tuaregs and Arabs, ethnic groups most associated with rebels who have controlled Mali's north, were being especially targeted.
The leaders of the Arab community from across Mali, meeting in the capital Bamako on Sunday, appealed for calm.
"The victory shouldn't be stained by acts of unnecessary revenge, which do nothing to help the war effort, and which blacken our victory and complicate our live together tomorrow," said Mohamed Mahmoud El-Oumrany. (Additional reporting By Bate Felix in Niono; Editing by Myra MacDonald)