Former Greek prime minister Costas Simitis, who ushered the country into the European Union's single currency in 2001, has died at his summer house in the Peloponnese at age 88, Greek media reports.
"With sadness and respect, I bid farewell to Costas Simitis, a worthy and noble political opponent, but also the prime minister who accompanied Greece in its great national steps," Greek Prime Minister Kyriakos Mitsotakis said in a statement on Sunday.
The government proclaimed four days of mourning and said his funeral would be at the state's expense, Greek state news agency reported.
Simitis, a law professor and a reformist, assumed leadership of the PASOK socialist party in 1996 and was prime minister until 2004.
Simitis had been vacationing at his summer residence close to Athens in the Peloponnese in recent days.
He was transferred unconscious to the hospital early in the morning where his death was confirmed, the director of the Corinth hospital told local media.
During his government, Simitis reduced the budget deficit and public debt to make Athens qualify for euro zone membership.
In 2012, three years after the Greek debt crisis erupted, he published a book criticising the handling of the crisis by Greek politicians and the EU.
In that book, called Derailment, he also accused the European Commission of turning a blind eye to overspending by his conservative successor.