Malian President Ibrahim Boubacar Keita promised on Tuesday to address deteriorating security caused by an Islamist insurgency and inter-ethnic clashes as he was sworn in for a second five-year term.

Hundreds of supporters and local politicians attended the ceremony in the capital Bamako, which followed Keita's landslide victory last month in an election marred by militant attacks and claims of fraud by his opposition rival.

Mali has been in turmoil since Tuareg rebels and loosely allied Islamists took over the desert north in 2012. French forces intervened the following year to beat back the militants, but they have since regrouped.

The regular attacks by militants linked to al Qaeda and Islamic State in Mali and neighbouring Niger and Burkina Faso have alarmed Western powers like France and the United States who have poured troops and air power into the region.

"This election is not the victory of one Malian against another, it is the victory of all of Mali," Keita, 73, dressed in a flowing white boubou robe and matching cap, told the audience.

"I chose to place the re-establishment of peace and security at an absolute level of priority," said the president, universally referred to as IBK, promising to revive the stalled implementation of 2015 peace deal with ethnic militia.

But the security situation has only deteriorated in recent months. Threats by jihadists forced nearly 500 polling stations - about 2 percent of the total - to remain closed during last month's run-off even as no major attack materialised.

A United Nations camp for peacekeepers near the northern town of Menaka came under rocket fire early on Tuesday, injuring the head of security and a police official, Malian army spokesperson Hama Ag Attaher told Reuters.

Violence between different ethnic groups in Mali's previously peaceful centre has also escalated. Armed men dressed as Donzo hunters killed a dozen Fulani civilians in the Mopti region last week, local sources said.

The security threat as well as general voter apathy reduced turnout in the run-off to 34 percent.

Keita's challenger, opposition leader Soumaila Cisse, also accused the president's camp of widespread vote rigging but Keita rejected those charges in his speech and called on the opposition to rally around him.