Paul Biya, who has been president of Cameroon for 43 years, was sworn in on Thursday for an eighth term, after a contested election that sparked mass protests in which several demonstrators died.

The 92-year-old Biya, the world's oldest head of state, won the October 12 with 53.7 percent of the vote, according to official results, against 35.2 percent for his main challenger, former government minister Issa Tchiroma Bakary.

He was sworn in at a ceremony in parliament in the capital, Yaounde, for a new seven-year term at the helm of the central African country.

"I will spare no effort to continue to be worthy of this trust," Biya told the gathering attended by local political figures but no foreign leaders.

"I fully understand the gravity of the situation our country is going through. I understand the number and severity of the challenges we face and I understand the depth of frustrations and the scale of expectations," he continued.

Closely fought election

Tchiroma, a former Biya ally turned opposition figure, stirred enthusiasm among young voters and continues to insist he is the true winner of the election, which was closer than expected.

Several people are reported to have died when security forces quashed opposition rallies just before and after Biya's win was announced on October 27.

Tchiroma has since urged supporters to stage "dead city" operations, closing shops and halting other public activities.

The response has been mixed, with the call being widely followed in Garoua and Douala but in Yaounde most shops remained open, children were at school and employees went to work.

Tchiroma had been confined to his home in Garoua after the results were announced, but on Tuesday, one of his spokespeople told AFP that he was "on the move."

Charges against Tchiroma

The government has said it plans to initiate legal proceedings against the opposition leader, denouncing his "repeated calls for insurrection."

It has acknowledged that people died in the unrest but has not provided a toll.

Both the European Union and the African Union have condemned the authorities' violent crackdown on protests, while the United Nations' High Commissioner for Human Rights has called for an investigation.

Biya is only the second person to lead Cameroon since independence from France in 1960.