Seven passengers have died after gunmen attacked a busy train between Nigeria’s capital, Abuja, and Kaduna city, hospital sources have told the BBC.
The gang mined the track, forcing the train, carrying 970 passengers, to a stop on Monday evening.
One passenger told the BBC that gunmen subsequently surrounded the carriages and opened fire.
An unknown number of passengers were abducted from the train, considered the safest way to get between the cities.
Kidnapping for ransom has become commonplace across Nigeria.
The Abuja-Kaduna highway is one of the most dangerous roads in the country as kidnappers are known to ambush vehicles at several points along the expressway.
Over the last few years, this has pushed many to avoid the 150km (93-mile) journey by road, opting for the rail link instead, which opened in 2016. It is more expensive but considered safer as the trains have armed guards on board.
This was the second time the rail line between the cities has been targeted in the last six months, but is by far the most serious, says the BBC’s Chris Ewokor in Abuja.
According to the BBC Hausa service, 22 people, who were injured in the attack on Monday evening, were being treated at a military hospital in Kaduna.
A senior security source told the AFP news agency that military personnel rushed to the scene.
“The attack has been repelled by the troops who deployed in time. The terrorists fled when the soldiers arrived. The train is bulletproof, this saved the passengers who lay still on the floor.”
The Nigerian Railway Corporation (NRC) has suspended operations along the route.
The rail line is a gateway for millions of people in north-western states who want to travel to Abuja and further south.
The authorities in Kaduna state said they were liaising with the NRC to find out where all the passengers were and who exactly was missing.
Armed gangs carrying out killings and kidnappings for ransom have continued to unleash violence, especially in northern Nigeria despite military bombardments of their hideouts.
Just last Saturday, they attacked Kaduna’s international airport.
To avoid Nigeria’s notorious kidnapping gangs, thousands of commuters pack onto trains each day between the capital, Abuja, and the city of Kaduna.