African leaders in Pretoria for President Jacob Zuma's inauguration will hold informal talks on the security situation in Nigeria, South Africa's government said on Saturday.

Nigeria's President Goodluck Jonathan is among more than 20 heads of state gathered for the event.

South African President Jacob Zuma vowed to spearhead a "radical social economic transformation" as he was sworn in for a second term before dignitaries and a cheering crowd of thousands on Saturday.

"Today marks the beginning of the second phase of our transition from apartheid to a national democratic society," he said, promising more black empowerment and a bigger economic role for the state.

The leader of Nigeria's Muslims on Friday announced plans to host a national day of prayer in the capital as part of an effort to overcome Boko Haram's brutal Islamist insurgency.

The Sultan of Sokoto, Muhammad Sa'ad Abubakar III, has invited Nigeria's prominent Muslim leaders to the National Mosque in Abuja on Sunday.

The United States is alone in helping Nigeria locate more than 200 schoolgirls kidnapped by Islamists, Secretary of State John Kerry said Thursday, despite help on the ground from Britain, France and Israel.

With 80 military personnel sent to neighboring Chad for intelligence, surveillance and reconnaissance missions, the United States is the biggest foreign participant in the effort against the militant group Boko Haram.

The United Nations blacklisted Boko Haram as an al-Qaida-linked terror group and imposed sanctions Thursday, a month after the it claimed the kidnapping of more than 200 schoolgirls in Nigeria.

The designation, immediately welcomed by Britain and the United States, came into effect after no objections were raised by the Security Council's 15 members.

Protesters on Thursday were taking their call for the release of more than 200 schoolgirls kidnapped by Boko Haram to Nigeria's president, as U.S. military personnel headed to Chad as part of the rescue effort.

Demonstrators said they were intending to march on Goodluck Jonathan's presidential villa in the capital, Abuja, to maintain pressure on the embattled head of state to secure the girls' safe release. 

The United States has deployed 80 military personnel to Chad to help regional efforts to rescue more than 200 schoolgirls kidnapped in neighboring Nigeria, President Barack Obama said Wednesday.

"These personnel will support the operation of intelligence, surveillance and reconnaissance aircraft for missions over northern Nigeria and the surrounding area," Obama said in a letter to Congress.

Britain said Wednesday that Nigeria's deadliest ever bomb attack, which killed at least 118 people, would strengthen the international community's resolve to defeat terror in Africa's most populous nation.

Islamist militant group Boko Haram was blamed for two car bombs that tore through a market in the central city of Jos on Tuesday, 20 minutes apart.

Rescue workers on Wednesday combed through the rubble of Nigeria's deadliest bomb attack after at least 118 people were killed in the central city of Jos, with Boko Haram blamed for the atrocity.

Emergency services picked through the burnt-out remains of vehicles and collapsed buildings in the New Abuja Market area of the city, where two car bombs exploded within 20 minutes of each other on Tuesday.

Twin car bombings in central Nigeria killed at least 118 people and brought entire buildings down Tuesday, in the latest affront to the government's internationally-backed security crackdown.

Nigerian President Goodluck Jonathan swiftly condemned the attack in the central city of Jos, calling it a "tragic assault on human freedom" and condemning the perpetrators as "cruel and evil".