Mali's main Tuareg factions say they will boycott talks with the government next week on implementing a 2015 peace agreement, dimming hopes of attaining peace in the West African country.

The main separatist groups in northern Mali - the Coordination of Azawad Movements (CMA) and Platform, a coalition of pro-government Tuareg - said they could not take part in the conference, explaining that it was not sufficiently inclusive.

"We cannot take part in a conference which, far from uniting, risks being divisive," the groups said in a statement on Saturday.

The 2015 peace accord was meant to draw a line under a conflict that has pitted nomadic Tuaregs in the north against the government in the south.

But the implementation of the agreement has been held up by bickering, while armed groups affiliated to al-Qaeda have exploited the security vacuum to step up attacks.

After months of delays and arguments, there had been some signs of progress in recent weeks with the return of state authority to some cities from which it had been absent since the Tuareg revolt began in 2012.

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In April 2012, a nomadic rebel group called the National Movement for the Liberation of Azawad (MNLA) seized control of an area larger than France before being ousted by al-Qaeda-linked groups who imposed a strict interpretation of Islamic law on the local population, carrying out amputations and executions.

In January 2013, France launched a military intervention in its former West African colony to stop the rebels' southward offensive.

Despite continued French troop deployments, a United Nations peacekeeping mission and years of peace talks, Mali remains beset by unrest and ethnic strife.

In recent months, joint patrols by fighters from the various armed factions and the Malian security forces have helped restore confidence, but tensions remain high.

Earlier this month, armed groups surrounded Timbuktu, once a popular tourist destination because of its fabled history of gilded Islamic empires that grew rich on trade connecting Africa's interior with its Mediterranean coast.

The armed groups were opposed to the return of state authority to the city, and no agreement has yet been reached to allow it to go ahead.