Nigeria has relaxed a curfew in parts of the northeast where its troops are mounting their biggest offensive yet against fighters from the group Boko Haram.

The army has sent thousands of extra troops to try to dislodge the well-armed fighters from territory they control around Lake Chad, along the borders with Cameroon, Chad and Niger.

A round-the-clock curfew had been imposed since Saturday over large parts of the city of Maiduguri and other parts of Borno state, at the heart of the Boko Haram insurgency.

The curfew had raised fears of a humanitarian crisis if food supplies were unable to get through.

Lieutenant Colonel Sagir Musa, a spokesman for Nigerian forces in Borno, said the curfew had been relaxed and would start at 6pm and end at 7am.

Traffic remained at a trickle in Maiduguri, as many frightened residents remained in their homes.

Bases bombarded

President Goodluck Jonathan declared a state of emergency one week ago in the states of Borno, Yobe and Adamawa, sending thousands of extra troops to the region.

War planes were used to destroy fighter bases in remote rural areas on Friday.

The military said it had re-established control in five remote towns in Borno considered to be Boko Haram strongholds.

The military has "secured the environs of New Marte, Hausari, Krenoa, Wulgo and Chikun Ngulalo after destroying all the terrorists' camps," a defence ministry statement said.

Boko Haram has said it is fighting to establish an Islamic state in mainly Muslim northern Nigeria, but has changed its demands several times.

Attacks carried out by the group and its conflict with security forces are estimated to have cost around 3,600 lives since 2009.

Jonathan offered an amnesty on Sunday to any Boko Haram fighters who lay down their weapons and surrender, although analysts say the state of emergency will further complicate efforts to resolve the conflict through dialogue.

The US, EU and rights groups like Amnesty International and Human Rights Watch are concerned the state of emergency will enable Nigeria's military to commit abuses against civilians.

The UN emergency relief agency and Niger's Red Cross said in a report that around 1,500 people had fled across the border into Niger in the past two weeks, but it had not yet been established what their nationalities were.

Source: Agencies