KANO, Nigeria (AFP) - Fighter jets have bombed the north-east Nigerian border town of Malam Fatori, controlled by Boko Haram Islamists, witnesses told AFP on Thursday.

Residents in the town of Bosso, which lies next to Malam Fatori but across the border in Niger, said the bombardment began early on Wednesday and lasted for several hours.

"At around 8am, we started seeing three military jets encircling Malam Fatori and soon after (they) began dropping bombs," said Idrissa Ari, a Bosso resident.

His account was supported by three others in Bosso but there was no comment from the Nigerian military on the operation.

There was also no initial word on casualties or whether Boko Haram fighters had fled the area.

Reaching locals inside Malam Fatori is difficult given the collapse of the mobile phone network on the Nigerian side of the border.

The residents who spoke to AFP reported that the raid was carried out by fighter jets from Chad but there was no confirmation from the authorities in N'Djamena.

The Boko Haram uprising has become a regional crisis, with the four directly affected countries - Cameroon, Chad, Niger and Nigeria - agreeing to boost cooperation to contain the threat.

A brutal attack this month on the Nigerian town of Baga, near Chad and Niger, killed several hundred people and raised fresh questions about the Nigerian military's capacity to face Boko Haram alone.

While it was unclear whether Chadian troops had begun operating in Nigeria, security sources said soldiers from Chad had arrived in Cameroon ahead of an expected campaign against the Islamists.

"The first Chadian soldiers were deployed yesterday (Wednesday) in Fotokol," a Cameroonian security source told AFP, requesting anonymity.

Fotokol is just 500m from the Nigerian town of Gamboru, currently controlled by Boko Haram.

The insurgents control large parts of Nigeria's Borno state, which shares borders with Cameroon, Chad and Niger.