ABUJA (AFP) - Nigeria's presidential election was on Saturday postponed on security grounds, handing a potential lifeline to the ruling party as it battles a persistent challenge from the main opposition.

The head of the Independent National Electoral Commission (INEC) announced the delay after a closed-door meeting in Abuja that followed a recommendation for postponement from security chiefs, who said the military needed more time to secure areas under Boko Haram control.

A new date for the poll has been set for March 28 for presidential and parliamentary elections. Gubernatorial and state assembly elections will be held on April 11, INEC's Mr Attahiru Jega said.

Mr Jega said security chiefs advised a six-week postponement from the planned Feb 14 date as troops would not be available because of operations against the militants in the country's troubled north-east. "If the security of personnel, voters, election observers and election materials cannot be guaranteed, the lives of innocent young men and women and the prospect of free, fair and credible elections will be greatly jeopardised," he told reporters.

President Goodluck Jonathan has been locked in a tight race with the main opposition candidate, former military ruler Muhammadu Buhari.

But with the campaign now extended, analyst Dawn Dimolo, of the africapractice consulting firm, said the advantage could swing in favour of Jonathan's Peoples Democratic Party (PDP).

The PDP, never out of power since Nigeria returned to civilian rule in 1999, has the power of incumbency and access to greater funds than Buhari's All Progressives Congress (APC).

The extension could allow the PDP to claw back votes but could equally boost the APC, which has repeatedly claimed that the government was trying to scupper the vote, said Dimolo.

The APC said on Twitter: "Even if the election is postponed, Buhari will still win."

Troops from Nigeria, backed by soldiers from Chad, Cameroon and Niger, have recently begun a joint fightback against Boko Haram insurgents because of increased fears to regional security.

Since the turn of the year, the militant group has increased the intensity of its campaign, in part to further undermine the democratic process, which it views as un-Islamic.

Mr Jega has previously conceded that voting would not go ahead in areas under Islamist control, raising questions about whether those displaced by the violence would be able to vote.

The APC has said the overall result will be in doubt if the hundreds of thousands of people made homeless by the violence in the insurgents' strongholds are disenfranchised.

Mr Jega said national security adviser Sambo Dasuki and defence chiefs were unanimous in agreement that "security cannot be guaranteed" on Feb 14.

"The security services needed at least six weeks" to conclude their operations and during this time would be concentrated in the northeast, leaving them unable to provide security elsewhere.

Mr Jega said INEC's concerns about security were not confined to the northeast.

Political commentator Chris Ngwodo said the argument about not having troops for the election was erroneous, as the police and national civil defence corps provide security on polling day.

Mr Jega had also been under pressure to delay polling because of increased fears about the distribution of permanent voter cards to 68.8 million registered electors.

As of Thursday, he said that 45,829,808 or 66.58 percent of cards had been distributed and that INEC was "substantially ready for the general election as scheduled".

But advice since then had left it in no doubt that "it would be unconscionable to deploy personnel and voters" without adequate security, he told a news conference in Abuja.

Election monitors, including from the West African bloc ECOWAS and the European Union, are already on the ground and the international community has urged Nigeria to hold the election.

US Secretary of State John Kerry, on a whistlestop visit to Nigeria last month, said it was "imperative that elections happen on time, as scheduled".

He suggested a link between peaceful and timely voting and further US help for the counter-insurgency.

Ms Dimolo said the delay would help with the logistics of distributing voters cards and could possibly cool heads in the process.

But she said postponement could also prompt a violent reaction from angered opposition supporters, who are hoping to inflict a defeat on the PDP for the first time in 16 years.

In 2011, some 1,000 people were killed in post-poll rioting and there have been fears of a repeat.

Mr Ryan Cummings, chief Africa analyst at Red24 risk consultants, said there was no guarantee that a planned new regional force would make significant gains against Boko Haram before the end of March.

"To dislodge Boko Haram from all of these areas in a period of six weeks would be an unprecedented feat," he said.

"But even if achieved, securing liberated territories would be a task in its own, particularly if multi-national forces withdraw their presence from Nigeria."