Malian security services have broken up a cell in the capital Bamako operated by one of the Islamist groups that had controlled northern Mali until a French-led military intervention this year, a police source said Sunday.

The security services arrested seven people last month when they smashed the cell belonging to the Movement for Oneness and Jihad in West Africa, (MUJAO), the source told Agence France Presse.

"Since the start of the week, we have the formal proof. The seven people detained last month in working-class neighborhoods of Bamako formed the first MUJAO cell in Bamako," the source said on condition of anonymity.

The police obtained the help of Malian State Security intelligence services, whose role was "decisive in dismantling the cell," the police source said. "The investigation continues."

No details about where the seven were being held was available, but the arrests were mentioned in a confidential report that an AFP journalist consulted in Bamako on Sunday.

The report said the arrests "led to the dismantling of the MUJAO cell in Bamako."

It said the seven were all Malian nationals between 16 and 57 years old who were all trained militarily and ideologically by the Islamists in the north.

"The attempts at infiltration in the south of Mali will probably multiply," the document said. "The dismantled MUJAO cell was supposed to commit attacks in Bamako."

MUJAO and other armed Islamist groups, including Al-Qaida in the Islambic Maghreb, occupied key towns in northern Mali for several months and enforced a harsh interpretation of Islamic law.

In January, fearing a move south by the Islamists, France led a military intervention involving Malian and African forces that has driven the Islamists from the key towns like Gao and Timbuktu.

But armed Islamists remain active in certain parts of the vast north and have managed at times to infiltrate Timbuktu to carry out suicide attacks.

The confidential report seen by AFP also said a French-Malian man named Moussa Thiam, 24, was among the Islamists killed during a suicide attack on March 20 in Timbuktu.