At least 36 people were killed and another 66 injured late Tuesday when two trains collided near the Greek city of Larissa, authorities said.

Several carriages were almost completely destroyed in the collision between a passenger train and a freight train just before midnight on Tuesday, with at least one car appearing to catch fire and trap passengers inside.

Emergency services raced to find survivors among the charred wreckage on Wednesday.

"I've never seen anything like this in my entire life," said one rescue worker, emerging from the wreckage. "It's tragic. Five hours later, we are finding bodies."

Several cars had overturned or caught fire when they came off the tracks in the impact, leaving a tangled mess of metal and shattered glass.

A police spokesman told AFP the 59-year-old station master had been arrested, and charges would be announced shortly.

Government spokesman Yiannis Economou said the two trains were left running on the same track for "several kilometers."

'Complete panic'

The passenger train, carrying 350 people, had been traveling from the capital Athens to the northern city of Thessaloniki.

Health Minister Thanos Plevris said most passengers were "young people," with the train carrying many students returning to Thessaloniki after a long holiday weekend.

"It was a nightmare ... I'm still shaking," 22-year-old passenger Angelos told AFP.

"Fortunately we were in the penultimate car and we got out alive. There was a fire in the first cars and complete panic."

"The collision was like a huge earthquake."

"I was stained with blood from other people who were injured near me," a passenger named Lazos told the newspaper Protothema.

Some 150 firefighters and 40 ambulances were mobilized for the response, according to Greek emergency services.

"The operation to free trapped people is underway and is taking place in difficult conditions, due to the seriousness of the collision between the two trains," spokesman Vassilis Vathrakogiannis told reporters.

He later said that 36 people have been found dead, while 66 injured were in the hospital, including six people in intensive care.

Some 194 people have been rescued so far.

'Stained with blood'

As morning broke Wednesday, two large cranes on the site were starting to clear parts of the wreckage as rescuers worked to free any passengers potentially still stuck in the damaged wagons.

One of the smashed carriages was lifted from a field next to the train tracks where it had landed after derailing, surrounded by scattered debris.

It is not yet known why the two trains collided in what local media is calling the worst "train accident that Greece has ever known."

"My thoughts are with the people in Greece this morning," tweeted the head of the European Council, Charles Michel.

"Shocked by the news and images of the collision of the two trains," he added.

Neighboring Türkiye also offered condolences after the deadly train crash. Foreign Minister Mevlüt Çavuşoğlu held a phone call with his Greek counterpart Nikos Dendias on Wednesday morning.

The regional Gov. Kostas Agorastos told the Skai TV channel the death toll was likely to be "very high" and warned that the first two carriages on the passenger train "no longer exist at all."

'Windows exploded'

On the local media site Onlarissa, a young woman said that the train "was stopped for a few minutes when we heard a deafening noise".

Another passenger told Skai television that "the windows suddenly exploded. People were screaming and were afraid."

"Fortunately, we were able to open the doors and escape fairly quickly. In other wagons, they did not manage to get out, and one wagon even caught fire," he added.

The president of the OSE train drivers' union Kostas Genidounias told AFP from the scene of the accident that the two trains had ended up on the same track and collided head-on.

He said the accident was "unimaginable" and "would have been avoided if the safety systems were working".

An emergency government meeting was organized after the crash and military hospitals in Thessaloniki and Athens have been put "on alert" in case they are needed.

A three-day period of mourning has been declared.