JOS, Nigeria: Two car bombs exploded at a bustling bus terminal and market in Nigeria's central city of Jos on Tuesday, and witnesses said dozens of people were killed.
No one immediately claimed responsibility for the twin car bombs, but they bore the hallmarks of Boko Haram, an Islamic extremist group.
The second blast came half an hour after the first, killing some of the rescue workers who had rushed to the scene that was obscured by billows of black smoke.
Dozens of bodies and body parts were covered in grain that had been loaded in the second car bomb, witnesses said. A Terminus Market official said he helped remove 50 casualties, most of them dead. He spoke on condition of anonymity because he is not allowed to give information to reporters.
"It's horrifying, terrible," said Mark Lipdo of the Stefanos Foundation, a Christian charity based in Jos., who could smell burning human flesh.
Photographs show a woman's body, legs blown off, on the edge of an inferno consuming other bodies, with a hand reaching out of the flames. Another woman, unconscious, was being carried away in a wheelbarrow on a road strewn with glass shards.
Tensions were rising between Christians and Muslims in the city, the capital of Plateau state in Nigeria's Middle Belt region that divides the country into the predominantly Muslim north and Christian south. It is a flashpoint for religious violence.
No one immediately claimed responsibility for the attack. Boko Haram has claimed other recent bomb attacks. Two separate bomb blasts in April killed more than 120 people and wounded more than 200 in Abuja, the nation's capital, including at a busy bus station. A suicide car bomber killed 25 people in northern Kano city on Monday. Police there detonated a second car bomb Monday. They said both would have killed many people but the first exploded before it reached its target of restaurants and bars in the Christian quarter of the Muslim city.
Lipdo said at least one of Tuesday's blasts could have been averted if authorities had acted in time. He said a white van that held the first bomb was parked for hours in the market place, raising suspicions of vendors and others who reported it to the authorities, but nothing was done.
He said authorities also had another warning of impending violence: a man with explosives strapped to his body was arrested on Saturday and told police that many militants had been ordered to plant bombs around churches and public areas in Jos.
President Goodluck Jonathan extended sympathies to affected families and "assures all Nigerians that government remains fully committed to winning the war against terror, and this administration will not be cowed by the atrocities of enemies of human progress and civilization," a statement said.
The Nigerian government and military's failure to curtail the 5-year-old Islamic uprising, highlighted by the mass abduction of nearly 300 schoolgirls and lack of progress in rescuing them more than a month later, has caused national and international outrage. Jonathan has been forced to accept help from several nations including Britain and the United States in the hunt for the girls, who were taken in northeast Nigeria. It also has brought massive attention to the shadowy extremist group, which is demanding the release of detained insurgents in exchange for the girls - a swap officials say the government will not consider.
Diplomats said Nigeria on Tuesday asked a U.N. Security Council committee monitoring sanctions against al-Qaida to add Boko Haram to the list, with an arms embargo and asset freeze.
The extremists are threatening to sell the girls into slavery if Jonathan does not free detained insurgents, which officials say Jonathan will not do.
Boko Haram wants to turn Nigeria into an Islamic state under Shariah law. Half of Nigeria's population of 170 million is Christian, as is most of the population of Jos. The militants have increased the reach of their attacks this year, and their deadliness.
On Christmas Eve in 2010, bombs allegedly planted by Boko Haram exploded in Jos, killing as many as 80 people.
Meanwhile, more than 300 people have been killed in assaults on towns and villages in recent weeks, and the extremists also are blamed for an attack on a Chinese camp in neighboring Cameroon last week in which one Cameroonian soldier was killed and 10 Chinese workers abducted.
Militants' attacks have been coming with increasing frequency despite a year-old military state of emergency in three of Nigeria's states to curtail the uprising.
The Senate on Tuesday voted to extend the emergency for another six months but only if Jonathan devotes more money to the military campaign and to better arming demoralized soldiers who say Boko Haram is better equipped A letter with the conditions was sent to the president.
More than 2,000 people have been killed in the insurgency this year in Africa's most populous nation, compared to an estimated 3,600 between 2010 and 2013.