At least 25 people were killed today when an explosion ripped through a Catholic church during Christmas Mass near Nigeria's capital city.
A second explosion went off later near another church in the restive city of Jos, raising fears that a radical Muslim sect was to blame.
There was no immediate claim of responsibility for the blasts, but the explosions come amid a wave of attacks in Nigeria by Boko Haram, which has been blamed for at least 465 killings this year.
Last year a series of Christmas Eve bombings in Jos that were claimed by the militants left at least 32 dead and 74 wounded.
Today's first explosion struck St Theresa Catholic Church in Madalla, a town in Niger state close to the capital Abuja.
Rescue workers recovered at least 25 bodies from the church and officials continued to tally those wounded in various hospitals, said Nigeria's National Emergency Management Agency.
The agency has already acknowledged it did not have enough ambulances on hand to help the wounded. An angry crowd that gathered at the blast site hampered rescue efforts as they refused to allow workers inside.
In Jos, a second explosion struck near a Mountain of Fire and Miracles Church. Gunmen later opened fire on police guarding the area, wounding one police officer. Two other locally-made explosives were found in a nearby building and disarmed.
The city of Jos is located on the dividing line between Nigeria's predominantly Christian south and Muslim north. Thousands have died in communal clashes there over the last decade.
The US embassy in Abuja issued a warning to citizens on Friday to be "particularly vigilant" around churches, large crowds and areas where foreigners congregate.
Several days of fighting in the north east between the sect and security forces had already killed at least 61 people.
In the last year, Boko Haram has carried out increasingly bloody attacks in its campaign to implement strict Sharia law across Nigeria, a nation of more than 160 million people.
Boko Haram claimed responsibility for a November 4 attack on Damaturu, Yobe state's capital, that killed more than 100 people.
The group also claimed the August 24 suicide car bombing of the UN headquarters in Nigeria's capital that killed 24 people and wounded 116 others.
While initially targeting enemies via hit-and-run assassinations from the back of motorcycles, violence by Boko Haram now has a new sophistication and apparent planning that includes high-profile attacks with greater casualties.
Boko Haram has splintered into three factions, with one wing increasingly willing to kill as it maintains contact with terror groups in North Africa and Somalia.