Cameroon's 92-year-old President Paul Biya has promised to restore order in the country gripped by post-election violence, as he was sworn in for an eighth consecutive term in office.

In his inaugural address, the world's oldest president offered condolences to victims of the protests and blamed those he called "irresponsible politicians" for the unrest.

"I can assure you, order will reign," he promised, saying it was pointless to plunge the country into crisis.

Following allegations of fraud during last month's election, Biya described the electoral process as satisfactory and praised the electoral body Elecam.

The nonagenarian won 54% of the vote, compared to the 35% of Issa Tchiroma Bakary, according to the official results. 

Tchiroma Bakary maintains he was the rightful winner of the poll and has accused the authorities of fraud, which they have denied.

The announcement of the result led to deadly protests across the country, which saw at least 14 people killed and more than 1,200 arrested, according to the National Human Rights Commission. Other institutions have presented a far higher death toll.

In his swearing-in speech at the country's parliament in the capital, Yaoundé, Biya congratulated the security forces for containing the protests but failed to address complaints of excessive use of force.

He insisted the election was now in the past, urging citizens to work with him on building a "united, stable, and prosperous" country.

The president promised to make issues affecting women and young people a priority, with a commitment to tackle corruption and security challenges which have marred his administration over the years.

Biya first came into power in November 1982, after the resignation of President Ahmadou Ahidjo. His critics say he has ruled the country with an iron fist since then.

Prior to the inauguration, several parts of the country were crippled by a general strike called by Tchiroma Bakary, especially in his strongholds of Garoua and Douala.

He said he would resist until his "victory" was recognised, and went on to urge foreign powers to impose sanctions on Cameroonian officials over the recent crackdown on protests and complaints over electoral fraud.

Judges at the Constitutional Council had dismissed eight complaints about the election, citing insufficient evidence of irregularities or a lack of jurisdiction to annul results.

Tchiroma Bakary, leader of the National Salvation Front party, was a former government information minister who broke ranks with Biya to challenge him for power.

He has refused to file an official complaint.