One of the favourites in Mali's presidential election took his campaign to the restive northeastern former rebel stronghold of Kidal on Wednesday, calling it a gesture of unity.

Kidal was being run by the National Movement for the Liberation of Azawad, a rebel group launched to fight for independence for Mali's Tuareg people, until it was opened to Malian authorities and troops under a ceasefire deal last month to pave the way for Sunday's vote.

"I'm in Kidal as part of the campaign to show that Kidal is part of Mali. We are all brothers and we must build together a country that is one and indivisible," Soumaila Cisse, a former minister and ex-leader of the West African Economic and Monetary Union, told AFP.

Cisse's main rival, former prime minister Ibrahim Boubacar Keita, had already been to the town, 1,500 kilometres (930 miles) from the capital Bamako, on July 15.

The government and the MNLA signed a peace accord on June 18 allowing Malian troops to enter Kidal to run security ahead of the election.

The ceasefire has largely been respected, although the town has been the scene of recent violent pro- and anti-army protests and clashes between black Malians and the lighter-skinned Tuareg community which left four people dead.

Election officials and a politician in the Kidal region were briefly abducted on July 20 by suspected MNLA members in Tessalit, 250 kilometres north of Kidal, although the rebel movement denied involvement.

Relations between the black majority and Arab and Tuareg minorities, already strained before a French-led military intervention launched in January to drive Al-Qaeda-linked Islamists from northern Mali, have deteriorated considerably in recent months.

Mali's transitional government hopes the election will begin the process of reunification and restore the constitutional order destroyed by a military coup in March 2012.

Successful polls in the divided Kidal region will be seen as a hugely symbolic step towards reconciliation after a crisis that saw Islamist extremists seize the west African country's vast desert north in the wake of the coup.

But the region's 35,000 voters are unlikely to affect the outcome in a country with an electoral roll of almost seven million.