A speeding and overloaded bus crashed into a truck parked by a road in northern Nigeria on Monday, killing 20 passengers, an official and a hospital source told AFP.
The bus had set off from Nigeria's second city of Kano and was headed to Potiskum, the commercial capital of Yobe state.
Potiskum has been attacked repeatedly by Boko Haram Islamists, and the insurgency has forced state officials to impose a dusk-to-dawn curfew in several areas.
The bus was reportedly speeding towards the city in order to beat the curfew when it crashed at roughly 5:00 pm (1600 GMT).
"A commercial bus carrying 22 passengers ran into a stationary truck" just outside Potiskum, said Sani Umar, an official with the state drivers union, noting that the vehicle was intended to carry just 17 people.
"The truck somersaulted several times on impact. ...We evacuated 20 dead bodies from the bus, with two seriously injured," he added.
He described speeding as the "likely cause," as drivers typically increase their speed as the curfew approaches to avoid being barred from entering the city when the military shuts off access at 6:00 pm.
A doctor at the Potiskum General Hospital, who was not authorised to speak to journalists, told AFP that 20 dead bodies had been brought in from the accident site.
Osuman Masari of the Federal Road Safety Commission in Yobe state said he had "received information about a ghastly motor accident outside Potiskum this evening involving a commuter bus."
"We don't have details at the moment because we don't have people on the ground," he added.
Road safety officials were forced to withdraw from the area following a spate of attacks blamed on Boko Haram, he said.
The Islamists have killed hundreds of people across northern Nigeria since 2009.
Parts of several states targeted by the insurgents have been placed under curfew.
Nigeria's roads are among the most dangerous in the world.
Badly maintained vehicles, poor roads and widespread reckless driving conspire to kill thousands in motor accidents across Africa's most populous country each year.