Kostas Karamanlis announced his resignation as Minister of Infrastructure and Transport after the train collision in Larissa that has left dozen's dead.
As he said, his resignation was something that he felt was his duty "as a minimal sign of respect to the memory of the people who left so unjustly and taking responsibility for the eternal mistakes of the Greek state and political system."
Statement by the Minister of Infrastructure and Transport Kostas Karamanlis:
"I have just returned from the scene of the railway tragedy in Tempi. The pain is unspeakable.
"It is a fact that we received the Greek railway in a state that does not suit the 21st century. In these 3.5 years, we made every effort to improve this reality. Unfortunately, these efforts were not enough to prevent such an accident. And this is very heavy for all of us and for me personally.
"When something so tragic happens, it is not possible to carry on as if it didn't happen. I have been in politics for a few years, but I consider it a necessary element of our democracy that the citizens of our country trust the political system. This is called political responsibility.
"For this reason, I am resigning from the position of Minister of Infrastructure and Transport. It is what I feel my duty to do as a minimal sign of respect to the memory of the people who left so unjustly and to take responsibility for the timeless mistakes of the Greek state and political system.
"From the bottom of my heart, I once again express my pain and support to the families of the victims."
The Pope has passed on his "heartfelt condolences" to the victims and their families, the Reuters news agency reports.
In a statement, the Vatican says Pope Francis is "saddened" by the news of the train crash in Greece and is praying for "everyone affected by this tragedy".
Cardinal Secretary of State Pietro Parolin said: "To the injured, the emergency workers and all those providing assistance, his Holiness imparts his blessing as a pledge of strength and solidarity in the Lord."
French President Emmanuel Macron has expressed his sympathy with those affected by the crash on Twitter.
“My thoughts are with the relatives of the victims of the tragic accident that happened last night near Larissa,” he writes in French and Greek.
“France is on the side of the Greeks.”
Η σκέψη μου είναι στους οικείους των θυμάτων του τραγικού δυστυχήματος που συνέβη χθες τη νύχτα κοντά στη Λάρισα. Η Γαλλία βρίσκεται στο πλευρό των Ελλήνων.
— Emmanuel Macron (@EmmanuelMacron) March 1, 2023
Kyriakos Mitsotakis has described the crash as "an unspeakable tragedy".
The Greek prime minister said it was "very difficult" and offered his sincere condolences to the victim's relatives.
Meanwhile, Greece will pay for the funerals of those who died in the train crash, the Greek government has announced.
The decision to pay for the services at public expense was taken by the minister of the interior Makis Voridis and minister of finance Christos Staikouras, according to local media.
So far, the authorities have confirmed the deaths of 36 people.
Flags on all public buildings in the country are flying at half mast and public events have been suspended as part of three days of national mourning.
The Greek fire department has said the number of people killed in the train crash is expected to rise.
According to the Greek newspaper Proto Thema, a spokesperson for the fire service said about 72 had been hospitalised.
He said identifying people was also proving "very difficult" because temperatures exceeded 1,300C where the fire broke out.
The station master of the city of Larissa has been charged with manslaughter by negligence.
Police say the 59-year-old has also been charged with grievous bodily harm by negligence.
The station master, who is in charge of signalling, denies any wrongdoing and has blamed the accident on a possible technical failure.
Investigators are trying to find out why the two trains were on the same track when they crashed near Larissa.