A weekend raid into Mauritania (search) by Algerian Islamic militants illustrates why north Africa (search) needs the U.S.-led joint counterterror exercises launched this week, a U.S. military spokeswoman said Wednesday.

The training exercise began Monday in Chad, Mauritania, Mali, Niger and, for the first time, Algeria, from where Islamic insurgents linked to the Al Qaeda network began a raid into Mauritania that left two dozen dead. Five other countries will take part by the time the program finishes in two weeks.

The Mauritania raid is an example of why nations in the region "have to work together now," said Maj. Holly Silkman, a spokeswoman for the Germany-based U.S. European Command, or EUCOM (search), which is responsible for operations in most of Africa.

"They're a threat to stability and security in this region," Silkman said of Algeria's Salafist Group for Call and Combat, which is listed by the Washington as a terrorist organization. "And the Africans are well aware of that."

On Tuesday, the Algerian group purportedly claimed responsibility for Saturday's surprise attack on a remote Mauritanian army outpost that left 15 Mauritanian troops and nine insurgents dead. The claim, posted on a Web site in Arabic, said the assault was a "hit against the Flintlock plan put in place by the enemy of God, America, and its agents in the region."

Flintlock is the name of U.S.-led, joint military exercises conducted by EUCOM every two years — this time in northern Africa with about 1,000 U.S. troops, mostly special operations forces, training about 3,000 African soldiers.

"Wherever there's an area we need to pay attention to, that's where Flintlock evolves and in this case, Africa is of growing strategic importance," Silkman said.

U.S. commanders are concerned terrorists could take advantage of Africa's little-policed deserts and jungles to set up shop. The regions are so remote and vast that Africa's relatively small, under-equipped and underpaid security forces have difficulty controlling them.

U.S. authorities also want to ensure that terrorists don't ply the same paths criminals and smugglers still use — centuries-old trade routes that crisscross the Sahara desert.

In 2003, U.S. forces began training armies in Mali, Niger, Mauritania and Chad as part of a U.S. State Department-funded program called the Pan-Sahel Initiative to help guard porous borders against terrorists and arms- and drug-trafficking. The Sahel straddles the southern edge of the Sahara desert.

EUCOM pushed to expand the initial $6 million program to Algeria, Tunisia, Morocco, Nigeria and Senegal and massively boosted its budget. It is now called the Trans-Sahara Counter-Terrorism Initiative, and is expected to be funded with $100 million a year for five years.

This year's Flintlock exercises are divided into two phases, Silkman said. In the first — in Chad, Mauritania, Mali, Niger and Algeria — 12-man U.S. special forces teams conduct infantry training with African units. These include live-fire rifle marksmanship, first aid, border patrol and airborne operations. They also instruct on human rights and the laws of land warfare.

On June 16, officials from all nine countries will participate in a "command post exercise" in which they'll be given a terrorism scenario and be asked to solve it together. The aim, Silkman said, is to improve collaboration between governments to keep terrorists from seeking sanctuary in the region.

"You're not going to be able to eradicate all kinds of radical terrorism, that's clear," Silkman said. "But realistically, what we're trying to do is get the countries to work together so that we can deny ... lines of communication, sanctuary, sustenance of any kind, be that water or food."

"If the terrorists or would-be terrorists are denied those things, then it's a safer environment for Africans and Africans are onboard with that. That's why they're coming to this exercise," she said.