Survivors have told of a "nightmarish 10 seconds" as their train carriage overturned and was engulfed in flames in a crash in central Greece.

At least 36 people died and dozens more were injured in the head-on collision between two trains near the city of Larissa on Tuesday night.

The front carriages of a passenger train involved were mostly destroyed.

"We heard a big bang," said 28-year-old passenger Stergios Minenis, who jumped to safety from the wreckage.

"We were turning over in the carriage until we fell on our sides and until the commotion stopped. Then there was panic. Cables, fire. The fire was immediate. As we were turning over we were being burned. Fire was right and left," Mr Minenis was quoted as saying by Reuters news agency.

"For 10, 15 seconds it was chaos. Tumbling over, fires, cables hanging, broken windows, people screaming, people trapped."

The passenger train had been travelling from Athens to the northern city of Thessaloniki when it crashed head-on with the other freight train, causing the front carriages to burst into flames, shortly before midnight local time.

It is being described as the worst train crash Greece has ever seen.

An investigation has been launched and police say they have arrested a local station master in Larissa.

Survivors have described the chaotic scenes after the crash, with one shaken passenger telling the BBC: "People were panicking and screaming - some people were afraid they were going to die."

Giannis Antonoglou, who escaped from the fifth compartment of the passenger train, said the windows suddenly smashed and "we ended up being tilted 45 degrees as if about to tip".

Another told Skai television he was lucky to escape his carriage "fairly quickly", but "in other wagons, they did not manage to get out, and one wagon even caught fire".

Some passengers said they were forced to break carriage windows with their bodies or luggage to escape the burning wreckage.

Angelos Tsiamouras told Greek broadcaster ERT the crash had felt like an earthquake, and he smashed the train window using his suitcase. "We broke the windows with our backs," another unnamed passenger said.

One survivor, Lazos, told the newspaper Protothema: "I wasn't hurt, but I was stained with blood from other people who were injured near me."

Many of the 350 passengers on board the passenger train were students in their 20s returning to Thessaloniki after a long weekend celebrating Greek Orthodox Lent.

Transport Minister Kostas Karamanlis said the exact number of dead is still unclear, amid reports there are 20-25 people still missing. However, officials say some may have left the scene without being accounted for.

Fire brigade spokesperson Vassilis Varthakogiannis said temperatures inside the first carriage reached 1,300C (2,370F), which "makes it hard to identify the people who were inside".

One woman told Greek channel ANT1 her 23-year-old cousin, who was speaking to his mother on the phone from the passenger train shortly before the line cut, is still missing.

"His mother has been looking for him since dawn," she added.

Sixty-six people were being treated in hospital for their injuries, including six admitted to intensive care.

"It was a very powerful collision," the regional governor of the Thessaly region, Kostas Agorastos, told state-run television.

He said the first four carriages of the passenger train were derailed, and the first two carriages caught fire and were "almost completely destroyed".

"They were travelling at great speed and one (driver) didn't know the other was coming," the governor added.

As daylight broke, dozens of rescue workers aided with cranes were lifting the charred remains of the derailed carriages to search for more victims.

"I've never seen anything like this in my entire life. It's tragic. Five hours later, we are finding bodies," an exhausted rescuer emerging from the wreckage told AFP news agency.

Greek Prime Minister Kyriakos Mitsotakis, who visited the disaster scene on Wednesday, has vowed to find out what happened and ensure it never happens again.

Police say they have charged the 59-year-old station master for the city of Larissa with manslaughter by negligence and grievous bodily harm by negligence. The station master, who is in charge of signalling, has denied both charges and blamed the accident on a technical fault.

Three days of national mourning have been declared.