Unidentified gunmen on Saturday attacked the central prison in Niger's capital, opening fire on the guards and fighting their way inside the complex, according to a state security agent who said he was 40 meters (yards) from the prison when the incident occurred.

Souleymane Magagi said he saw more than one guard fall, though he could not be sure whether they were wounded or dead, because he had to run for cover. Magagi said the fighting started at around 3:30 p.m. local time and continued inside the prison, where he said several fighters from the Nigerian extremist group, Boko Haram, were currently incarcerated.

"Armed men came and attacked the central prison. They shot at the guards and were able to penetrate the prison, probably to liberate their colleagues. They are likely elements of MUJAO and Boko Haram," he said.

An Associated Press reporter who rushed to the scene was unable to get close because the roads leading to the prison had been roped off. The prison attack comes less than two weeks after Islamic extremists carried out one of the boldest attacks in recent years when suicide bombers infiltrated the Nigerien towns of Agadez and Arlit, and succeeded in detonating explosives inside a military camp and a French-operated uranium mine, killing 35 people, include the jihadists. Both those attacks were claimed by the Movement for Oneness and Jihad in West Africa, or MUJAO, and by "Those Who Sign in Blood," the six-month-old terror cell of Algerian jihadist Moktar Belmoktar, who earlier carried out the Jan. 16 assault on a BP-operated gas plant in Ain Amenas, Algeria.

The number of casualties in the prison attack could not immediately be confirmed, and government numbers rang unanswered.

If Magagi's assessment is correct, and the attackers include both MUJAO and Boko Haram members, it will be the first conclusive evidence that the Mali-based and the Nigerian-based extremists are working together. Analysts have long warned that the disparate radical groups in the band of countries at the base of Africa's Sahara desert are sharing training and know-how and plan to carry out joint operations, laying the groundwork for an "arc of instability" that will stretch from Mauritania on the continent's Atlantic Coast, all the way to Somalia, on its eastern Indian Ocean seabord.