Wednesday, the Greek Prime Minister Kyriakos Mitsotakis visited the site of the train wreckage near Larissa, Greece, accompanied by rescue workers and members of the Greek military.

"I can guarantee one thing. We will learn the causes of this tragedy and we will do anything possible so that it never happens again," he said.

Opposition leader Alexis Tsipras who is also visiting the site, speaks of an "unimaginable tragedy" that includes "many young people".

In Greece's worst train tragedy in decades, two carriages were crushed and a third engulfed in fire when a passenger train and freight train collided in the central city of Larissa.

A head-on collision between two trains in Greece killed 36 people, with many more still missing Wednesday after the accident on a route plagued by years of safety warnings.

In Greece's worst train tragedy in decades, two carriages were crushed and a third engulfed in fire when a passenger train and freight train collided in the central city of Larissa.

At least 85 people were injured in the accident, which left a tangled mess of metal and shattered glass in a field. Six of them are in intensive care.

"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."

In some cases, passengers are being identified from body parts, volunteer fireman Vassilis Iliopoulos told Skai TV, warning that the death toll would rise.

"It was the train of terror," Pavlos Aslanidis, whose son is missing along with a friend, told reporters.

Greece's transport minister submitted his resignation just hours after the accident.

"When something so tragic happens, we cannot continue as if nothing had happened," Kostas Karamanlis said in a public statement.