Three girls have staged suicide bombings in the Nigerian city of Damaturu, killing at least 13, as people prepared for the Eid festival at the end of Ramadan.
The attacks, in a northeastern area hard hit by the Boko Haram insurgency, comes just days before Nigeria's new President Muhammadu Buhari travels to Washington for talks with US counterpart Barack Obama.
The country's new army chief Major General Tukur Buratai was also due to visit Damaturu on Friday (local time) to celebrate Eid with soldiers battling Boko Haram.
Buhari is expected to use Monday's meeting with Obama to push for US help to tackle the jihadist violence, which has surged since he took office in May, claiming more than 700 lives.
Boko Haram have increasingly used young women and girls as human bombs over the past year as part of a campaign of terror that has left 15,000 people dead and 1.5 million homeless since 2009.
In a sign of how the violence is spreading across the region, a soldier and 19 Boko Haram members were killed in a shootout following an insurgent raid on an army post at Lake Chad, a security source in neighbouring Chad said.
In the Nigerian attacks, residents said twin explosions near a prayer ground in Damaturu killed two people, before a third blast moments later near a mosque that left another 11 dead.
Markus Danladi, Yobe state police commissioner, confirmed 13 people were killed.
"The attacks were carried out by three underage girls. Fifteen people were also injured in the attacks."
Army spokesman Sani Usman however gave a toll of nine dead and 18 wounded.
This year's Ramadan has been particularly deadly in Nigeria, with suicide bombers hitting mosques and worshippers gunned down as they prayed.