With just three weeks to go before Nigeria's presidential election, major cash and fuel shortages are stirring up public anger and tensions during campaigning for the country's top post.

Candidates have traded accusations of blame over the shortages with the ruling party hopeful even suggesting his enemies had manufactured the crisis to undermine his election chances.

Campaign rhetoric has been heating in the run up to the February 25 vote to decide on the successor to President Muhammadu Buhari, a former army commander who steps down after two terms in office.

The election appears close with three leading candidates: Bola Tinubu of the ruling party All Progressives Congress (APC), main opposition party Peoples Democratic Party's (PDP) Atiku Abubakar and Labour party hopeful Peter Obi.

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The naira currency exchange has caused cash shortages and queues outside ATMs and banks / © AFP/File

Already grappling with widespread insecurity and economic fallout from the Ukraine war, Nigerians are also dealing with fuel shortages and limited access to cash due to a programme to exchange old bank notes for new ones.

One of Africa's top oil producers, Nigeria often struggles with fuel shortages as it imports most of its petrol and diesel because its refineries are not working.

Across the nation, people have been sleeping in cars outside petrol stations for a chance to fill their tanks while crowds jostle outside ATM machines and banks to try and access scarce cash supplies.

Earlier this week, riots broke out in the northern city of Kano, with an angry mob protesting a visit by Buhari and blaming the ruling APC for the currency hardship.

Tinubu, a former Lagos governor, has lashed out at enemies for purposefully creating the crisis to derail his own election.

"They are trying to cause trouble and sabotage us," Tinubu told supporters at a rally in Abeokuta last week. "Whether there is fuel or not... we will vote and win."

But powerful APC governor for Kaduna State, Nasir El-Rufai, stirred up tensions further this week with a claim "saboteurs" in the presidential villa were trying to undermine Tinubu.

"We are convinced there are some elements in the villa that want the APC to lose the election," El-Rufai told Arise News.

"There appears to be very strong evidence of a conspiracy to incite voters against the APC."

After meeting with APC governors concerned about the political fallout from the crisis, Buhari on Friday urged Nigerians to give him seven days to make a decision on the currency swap to help ease shortages, according to a presidential statement.

- 'Godfather of Lagos' -

Known as the "Godfather of Lagos" for his political influence, Tinubu was instrumental in getting Buhari elected in 2015 and re-elected in 2019.

But he has rattled APC ranks with his claim "It's my turn" for the presidency.

Information Minister Lai Mohammed told reporters he was unaware of anyone in the presidency working against Tinubu and said Buhari just wanted a free, fair and credible contest.

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Nigerian President Muhammadu Buhari steps down after two terms in office / © AFP/File

But PDP candidate Abubakar's campaign was quick to point to Tinubu trying to distance himself from the Buhari government's record over eight years.

"Tinubu ought to know that Nigerians can see through his antics and beguilements and that his diversionary theatrics on fuel and new naira notes cannot sway Nigerians at this moment," PDP spokesman Kola Ologbondiyan said in a statement on Twitter.

Since emerging from military rule in 1999, Nigeria's elections have often been marred by logistical problems, violence and claims of fraud.

The Independent National Electoral Commission or INEC this week said it was concerned fuel shortages may also disrupt its organisation of the ballot.

The central bank on Thursday authorised banks to start distributing new naira currency notes in a bid to ease the cash shortages.

First elected in 2015, Buhari promised to end a long war against jihadists in the northeast.

But although Islamist militants have been driven out of swaths of territory they had controlled, the war is grinding on in the northeast. More than two million people have been displaced.

Insecurity has also spread. Criminal militias in the northwest and central regions often carry out mass kidnappings and looting raids on villages.