Greek Prime Minister Kyriakos Mitsotakis has blamed human error for a collision between two trains that killed at least 38 people, in the country's worst rail catastrophe that caused the resignation of the transport minister.

On Tuesday night, outside the central city of Larissa, a passenger train travelling from Athens to Thessaloniki collided with a freight train from the northern city of Thessaloniki.

Some of the passenger carriages erupted in flames from the crash.

"Everything shows that the drama was, sadly, mainly due to a tragic human error," Mitsotakis, seeking re-election this year, said in a televised address on Wednesday.

According to Hellenic Train, the passenger train left Athens at 7:22 p.m. and carried approximately 350 persons (19:22 GMT).

Greece's transport minister, Kostas Karamanlis, resigned after visiting the disaster site, citing a sense of "duty" to do so.

"The suffering is indescribable," he remarked. "When something so tragic happens, it is impossible to carry on as if nothing happened.

"I consider it a necessary element of our democracy that the citizens of our country trust the political system. This is known as political accountability."

At least 66 people were injured, including six in extreme care. At the same time, approximately 250 passengers, some with minor injuries, were evacuated safely by bus to Thessaloniki, about 130km (80 miles) away.

Medical units used to treat burn victims in the region were informed, and scores of ambulances were deployed to the scene.

Stergios Minenis, a 28-year-old passenger who jumped to escape from the wreckage, stated, "We heard a loud bang, [it was] 10 nightmare seconds."

"We were turning over in the wagon until we fell on our sides … then there was panic, cables [everywhere;] fire, the fire was immediate, while we were turning over we were getting burned, the fire was right and left."

"I've never seen anything like this before."

Earlier, the office of Prime Minister Mitsotakis established a three-day national period of mourning.

Meanwhile, Greek President Katerina Sakellaropoulou said she would return to Greece early from visiting Moldova.

"Unfortunately, I must interrupt my visit to be close to my people and assist those in need," she said beside Moldovan President Maia Sandu at a joint news conference in Chisinau.

Governor of the Thessaly region, Konstantinos Agorastos, stated that two trains were speeding towards each other on the same track.

"They were travelling at great speed, and one [driver] didn't know the other was coming," he added.

The first four carriages of the passenger train were derailed in the incident, with the first two carriages, which caught fire, "almost destroyed", Agorastos said.

Television video depicted derailed wagons with freight containers inverted and roadside debris strewn everywhere. Rescue personnel equipped with powerful torches were scouring through the debris for passengers who had become trapped. Some were searching for survivors in the adjacent fields.

"We are experiencing a tragedy. People are being rescued alive, injured, and dead. "We're going to be here all night until we're done or until we find the last person," a volunteer rescue worker told ERT.

Wednesday before dawn, rescue personnel illuminated the site with floodlights as they desperately searched the mangled, burning wreckage for survivors.

"I have never before witnessed anything like this in my entire life. It's a tragedy. "Five hours later, we are finding bodies," a tired rescuer exclaimed as he exited a carriage.

After the collision, an emergency government meeting was convened, and the Greek health minister, Thanos Plevris, rushed to the scene.

A young man evacuated to a neighbouring bridge told SKAI TV, "There was panic in the carriage, and people were screaming."

Lazos, a passenger, told the publication Proto Thema that the event was "very shocking."

"I wasn't injured, but I was covered in blood from nearby victims," he explained.

As part of its international bailout package, Greece transferred railway operator TRAINOSE to Ferrovie dello Stato Italiane in 2017 with the expectation that hundreds of millions of euros would be invested in rail infrastructure.