Western donors have pledged nearly $2.3 billion in funding aimed at preventing terrorism and lawlessness along the southern rim of the Sahara, the head of the G5 Sahel grouping said on Thursday.

"These pledges from our partners broadly cover the overall needs" of around 40 development projects to fight jihadism in the region, Niger President Mahamadou Issoufou told reporters after a donor conference in the Mauritanian capital Nouakchott.

The five Sahel states - Mauritania, Burkina Faso, Chad, Mali, and Niger - have been struggling against extremism and lawlessness in the Sahel since a jihadist revolt that began with a Tuareg separatist uprising in northern Mali in 2012.

The EU's International Cooperation and Development Commissioner Neven Mimica had told the conference that the bloc's Sahel Priority Investment Programme (PIP) had reached almost $910 million with an extra $138 million announced on Thursday.

French Foreign Minister Jean-Yves Le Drian said Paris would add an extra 220 million euros to 280 million euros already pledged, for a total of 500 million.

"Half of this sum is for projects already planned or under way. The other half will be awarded in a speedy way over the next two years to enable you to meet your priorities," Le Drian told the conference.

The five Sahel countries had sought $2.1 billion to help them fund projects in border regions vulnerable to jihadists. They themselves provide 13% of that sum.

Governments hope that with an array of projects, including building schools and health centres and improving access to water, they can prevent communities from falling under the influence of extremists.

Jihadism in the region has been fuelled by the chaos that engulfed Libya in 2011, the Islamist takeover of northern Mali in 2012 and the rise of Boko Haram in northern Nigeria.

The extremists were largely driven out of Mali in a French-led military operation launched in January 2013.

The France-backed fledgling African regional force fighting jihadists is also suffering from lack of funding, and shortfalls in equipment and training have led to delays in its operations.

As well as fighting terrorism it tackles smuggling and illegal immigration networks that operate in these vast, remote areas on the Sahara's southern fringe.

A devastating attack in June on the force's headquarters in Mali, claimed by an al-Qaeda-linked group, destroyed the communications room, prompting a brief halt in operations.