Police and residents search for victims after the two trains collided in Petarukan in Central Java Photo: REUTERS
Rescuers spent hours searching through the mangled wreckage for trapped survivors of the accident, which occurred just before 3am, as many passengers were sleeping.
A train from the capital, Jakarta, ploughed into the rear of a train that was sitting at a station in Petarukan, a coastal city in Central Java province.
The force of the crash knocked several carriages off the track, and twisted debris from the train littered the area.
"Bloody corpses were hanging from the carriages," said Anwar Sumarno, a 24-year-old university student who had been sitting near the front of the stopped train.
"The injured were screaming in the darkness, but there was nothing we could do," he said. "Everyone was in a state of shock."
It took almost an hour for rescue workers and ambulances to arrive.
Villagers and railway officials used their bare hands and bamboo sticks to search for survivors. Eventually, heavy cranes arrived to help move slabs of metal, helping speed rescue efforts.
Investigators were trying to determine if human error was to blame.
"It may also have been mechanical," said Bambang Ervan, the transport ministry spokesman. "We're checking to see if the signals of the parked train were working properly."
Indonesia – with a reputation for poor safety standards and maintenance – has been hit by a series of plane, train and ferry accidents in recent years that have killed hundreds.
Just an hour after Saturday's collision, another train crashed in the town of Solo, also in Central Java, killing at least one person.