Two trains collided outside the Indonesian capital Jakarta late Monday, killing at least four people, injuring dozens, and prompting a mammoth rescue effort.

One survivor while narrating the horrific moments after a long-distance train slammed into the stationary commuter train said people were trapped inside mangled carriages.

She said she was on her way home from work, when her train stopped at the Bekasi Timur station some 25 kilometres from Jakarta.

She said she had feared suffocating to death in the human pileup, and worried that some pinned underneath didn’t make it.

According to spokesman Franoto Wibowo of the KAI state-owned rail compnay, a taxi appears to have clipped the commuter train on a level crossing, causing it to come to a standstill on the tracks, where it was hit.

At the station, chaotic scenes unfolded in the aftermath of the crash, with rescue workers shouting for oxygen tanks as ambulances stood by in a snaking queue, lights flashing.

Reporters at the scene witnessed people being carried out of the wreckage on gurneys and loaded into waiting ambulances as hundreds of bystanders looked on, some seemingly in shock.

Another KAI spokeswoman, Anne Purba, told reporters at least four people had died and some 38 were hospitalised.

As rescuers worked to free many more trapped in the crushed train carriages, deputy house speaker Sufmi Dasco Ahmad said the toll could rise.

The military, fire brigade, the national search and rescue agency and the Red Cross were aiding in the evacuation effort.