Displaced people in north-east Nigeria have told the BBC they were transported through a dangerous conflict zone ahead of the country's elections in an operation agreed by the main political parties.

The BBC has been told that the unescorted convoys were organised with the agreement of both the ruling and main opposition parties, and the electoral commission.

Several thousand displaced people are believed to have been moved back to their home areas temporarily in order to vote.

Nigerians had been due to vote on 16 February but the polls were postponed until this Saturday.

Several witnesses described how displaced people had been organised into what they said was an unescorted convoy to make the journey from Maiduguri, the capital of Borno state, to the town of Monguno - a journey of 140km (87 miles) through territory which is known for attacks by Boko Haram and Islamic State in West Africa (Iswap).

Over the years, violence across the state has driven thousands to seek shelter in Maiduguri. But this, say senior officials from both the ruling All People's Congress (APC) and the opposition People's Democratic Party (PDP) creates logistical difficulties for those organising these elections because they would have to provide separate voting centres for each displaced group.

Nearly two million people have been forced from their homes by the fighting

Officials decided that the larger groups could go back home to vote, if their towns were deemed safe.

Many of the displaced were originally from Monguno and had been uprooted in earlier attacks.

The BBC spoke with two men who said they were part of a convoy of buses and lorries which travelled from Maiduguri to Borno in the days before the election was originally due to take place.

At their request we have protected the men's identities.

"Mamdu", a farmer and father of eight children, said that there were 10 buses and three lorries. He estimated that each bus carried between 90 and 96 people.

We asked if they were afraid and whether Boko Haram operated on that road.

"Yes there is," he replied. "The road is very dangerous and it is only God that protects."

We asked him why he had made the journey.

He said he had been offered 20,000 naira (almost $55; £42) by representatives of the ruling APC to vote for the party in Monguno. He said he was first given 2,000 naira as an allowance, with more to come after the voting.

"It's because of the poverty we are facing," he replied, "and they promised to give us 20,000 each - that's why we decided to go with them".

"Ibrahim" said he was afraid on the journey and that people had been complaining that day because there was no water and there was no escort.

He too said he had gone because "I have family, thinking that the money I will get will help and solve some of my problems".

He said there was no arrangement about returning.

A vehicle was sent and the displaced "fought and rushed before we got in the car - and some of them are still in Monguno".

Isa Gusau, a spokesman for the state governor, rejected allegations of cash inducements, saying there was no need to offer money as the opposition had "near zero" chance of winning in the area.

Paying for votes 'routine'

The ruling party is by no means alone in facing allegations of using cash to induce people to vote for its candidates.

Allegations of vote buying by the main parties are routine in elections in Nigeria, where power depends on wide networks of influence.

The opposition PDP has also been accused of spending large amounts of money to buy votes.

A reliable source in the town of Gwoza, about 130km south-east of Maiduguri, told the BBC that both main parties had offered money to displaced people in order to secure their votes.

According to the BBC's sources, the displaced were taken to two schools in Monguno - the Central Primary School and UBE Primary School - and an open area in the community.

Senior sources in several international organisations have confirmed that their staff on the ground had received similar reports from internally displaced people (IDPs).

According to these sources several thousand people may have been moved between different locations in order to vote.

Moving people to vote has increased overcrowding in this camp in Monguno, a relief worker told the BBC

One relief worker told the BBC that Monguno was already overcrowded with displaced people.

More than 8,000 IDPs were affected when a fire broke out in one crammed camp in the town on 8 February.

"In addition to the security implications of this arrangement, with convoys being vulnerable to attacks, it is increasing the pressure and overcrowding in Monguno - now for an extended period - where thousands of IDPs are already existing in unacceptable conditions.

"After the elections, we are concerned that these people will just be abandoned where they are," the source said.

'Attempt to win voters'

Responding to questions from the BBC, the state governor's spokesman, Mr Gusau, confirmed that displaced people had been moved between Maiduguri and Monguno and vice versa.

He said that this had been agreed with the Independent Nigerian Election Commission (Inec) and all political parties.

"Rather than Monguno have two voting centres, one in Maiduguri and another in Monguno where majority of voters are, it was best to transport Monguno voters to Monguno to join the majority and vote there… all in an effort to make the election smooth."

Mr Gusau said life had returned to Monguno and it was now "accessible to everyone".

The PDP's candidate for the seat of governor also defended the move.

"Most of the people who are registered to vote in Monguno are already there, whether as residents or as IDPs from neighbouring areas," said Mohammed Imam.

"So bringing the other 10 or so percent in will simplify the voting process."

There was, he said, no official plan on how to move those travelling to vote, which provided the opportunity for politicians to step in and provide transport in an added attempt to win over potential voters.

A group of candidates from smaller parties in Maiduguri has claimed that the movement was "a ploy to deny other candidates the opportunity to campaign to the IDPs".

The group of six parties said "people were brought to Maiduguri because of the security situation in their respective local governments.

"But to our astonishment, they were moved to other locations outside the state capital."

They pointed to recent violence, including an ambush on the convoy of the state governor, Kashim Shettima, on Tuesday 12 February - four days before the election was due to be held.

Three people were killed, according to the government, although some officials speaking anonymously say there were dozens of deaths.

On 16 February a suicide bomber and gunmen attacked a mosque in Maiduguri killing 11 people. Two days later, 14 people were killed when a group of wood gatherers was ambushed about 10km from the city.

Boko Haram and Iswap attacks have spread in recent months in the north and east of Borno State, in spite of claims from the Nigerian military that only small pockets of the jihadists remain.

The country director of Amnesty International, Osai Ojigho, has called for an investigation and said she is concerned that IDPs had been put risk.

She said the displaced were people who had already been traumatised by the Boko Haram insurgency.