BAMAKO (Reuters) - Suspected Islamist militants freed 93 prisoners during an attack on a jail in the central Mali town of Niono early on Tuesday, officials said.

The prison break was the second of its kind in recent weeks in Mali, where militant groups based in the desert north have extended their campaign into central and southern regions, complicating international efforts at peace.

Five armed men attacked the jail at around 0115 GMT, injuring two guards, the Ministry of Security said.

Ninety prisoners remained at large on Tuesday afternoon; three were re-captured. The army was deployed in pursuit.

It was not immediately clear who was behind the attack, but a number of Islamist groups, some linked to al Qaeda, have stepped up their insurgency in Mali this year.

Army spokesman Diarran Kone said the attack bore the hallmarks of followers of radical Islamist preacher Amadou Koufa, the leader of an ethnic Fulani jihadist group, the Macina Liberation Front. It was unclear whether any suspected jihadists had been in the prison.

Last month, gunmen broke into a prison in southern Mali, freeing 21 inmates. But the two prisoners they had aimed to release had already been moved away, authorities said.

Islamist groups hijacked a separatist Tuareg rebellion in 2012 to seize towns in Mali’s vast desert north. French forces drove them back a year later, but they have since reorganized, and in recent months launched dozens of attacks.

At a security forum in Dakar on Tuesday, French and American officials expressed concern about the spreading violence.

“It is not so much North Mali that worries us in the short term as the increase of violence towards the south of the country,” Vice Admiral Michael Franken, deputy commander for the military operations of Africom, told Reuters.