Speaking after a meeting Friday between the four army heads, a Malian officer who attended said: "The situation in Libya is of great concern. There is a risk of destabilising the entire region."
The meeting was to reinforce the fight against insecurity in a region threatened by Al-Qaeda in the Islamic Maghreb (AQMI).
"Moreover, because of the Libyan crisis, the security situation in the Sahel has deteriorated, so it is necessary to be careful. We are all on alert and we keep each other informed," he added.
According to a document from one of the participating countries, seen by AFP, "there is now no doubt, several Al-Qaeda fighters are involved in the Libya fighting."
These included "Libyan Islamists who were released by the government a few weeks before the outbreak of the conflict" in mid-February.
The paper adds that among the insurgents fighting Moamer Kadhafi's regime are Libyan combatants from Afghanistan and those who had fought for AQMI in the Sahel.
It urged Sahel countries not to allow weapons from Libya to fall into the hands of "terrorists in the Sahel" and strengthen the Al-Qaeda army.
In late March, Mali and Niger security sources said AQMI had taken advantage of the Libyan conflict to accumulate heavy weapons, such as anti-aircraft missiles, described as "a real danger for the whole area."
The vast Sahel desert zone is a base and hunting ground for AQMI which has stepped up activities in recent years, carrying out kidnappings of mostly foreign citizens, executions and drug trafficking.