More than 100 people were killed Tuesday in a pair of bombings at a bus terminal and adjacent market in the busy central Nigerian town of Jos, the latest in a series of attacks that has the country reeling.
The detonation of two vehicle bombs within half an hour seemed calculated to exact maximum casualties. Although the tactic has been used by terrorist groups in other parts of the world, it was the first attack of its kind in Nigeria.
The blasts came two days after a suicide attacker set off a car bomb on a street lined with bars in the major northern city of Kano, killing four people. Police in that city averted another attack when an explosive device was found in an abandoned car on Monday, according to local news reports.
There is also mounting frustration about the government's seeming inability to rescue 276 schoolgirls abducted last month by Islamic extremists in northeastern Nigeria.
The first blast in Jos, in the bus terminal, killed about 10 people, according to local media. Scores more died in the explosion in the crowded market. The National Emergency Management Agency put the combined toll at 118.
Police said the explosives were concealed in a minibus and a car. There was no immediate claim of responsibility for the attacks.
Jos, in Plateau state, has often been associated with sectarian violence. The city is situated at the crossroads between the mainly Muslim north and predominantly Christian south.
Tuesday's attack took place in a predominantly Christian part of the city. But car bombs have not typically been used in the region's communal violence. Suspicion was likely to be directed at the Islamist militia Boko Haram, which has carried out similar attacks and claims to be holding the kidnapped schoolgirls.
The recent surge in violent attacks -- and casualties -- has raised fears that the group is expanding its area of operation. Most of its attacks had been carried out in the northeast.
Designated a terrorist organization by the United States, Boko Haram has a cell-like structure and has become increasingly aggressive under its current leader, Abubakar Shekau. Its targets include schools, churches, bus terminals and markets.
Two car bombings in the capital, Abuja, have killed at least 120 people since last month. Boko Haram claimed responsibility for the first of them, an attack on April 14 that killed 75 people.
The same day, the group attracted international headlines with its abduction of more than 300 schoolgirls from the town of Chibok, some of whom managed to escape.
As the Nigerian military has grappled with how to free the girls without them being killed, there have been near-daily reports of fresh attacks.
"The 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," he said in a statement.
Jonathan also said that his government was determined to take every step necessary to secure the release of the abducted schoolgirls. A presidential committee plans to visit Chibok on Wednesday on a fact-finding mission.
Nigerian lawmakers on Tuesday extended a state of emergency in three northeastern states where Boko Haram is most active.