Many commentators in Africa and beyond have linked the al Qaeda attack with the French military action in Mali aimed at stemming the terrorist control of the country's vast desert.
Mr Cameron told MPs: "What we know is the terrorist threat in the Sahel comes from al Qaeda in the Islamic Maghreb. They aspire to establish Islamic law across the Sahel and northern Africa and they also aspire to attack western interests in the region and wherever they can."
With echoes of Tony Blair and his talk of terrorist threats from Iraq and Afghanistan, the PM stressed Mali had become a safe haven for al Qaeda.
Mr Cameron explained how the scale of the al Qaeda threat had been reduced in some parts of the world, such as Afghanistan and Pakistan, but was now growing in other parts of the world. "We need to be equally concerned about that and equally focused on that," he insisted. "There is a great need, not just for Britain but for other countries, to give a real priority to understanding better and working better with the countries in this region.
"Those who believe somehow there is a terrorist, extremist, al Qaeda problem in parts of North Africa and it's a problem for them and we can somehow back off and ignore it, that is profoundly wrong.
"We need to be absolutely clear about that, particularly in support of the French action in Mali where it is vital we do not allow an al Qaeda-sponsored regime to take over."