CHP leader Kilicdaroglu called the march after lawmaker Enis Berberoglu was sentenced to 25 years in jail on Wednesday
Turkey's main opposition leader on Sunday vowed to press on with a "walk for justice" from Ankara to Istanbul after President Recep Tayyip Erdogan warned he risked facing legal proceedings for the action.
Republican People's Party (CHP) leader Kemal Kilicdaroglu called the march after former journalist turned CHP lawmaker Enis Berberoglu was sentenced to 25 years in jail on Wednesday for leaking classified information to a newspaper.
Kilicdaroglu on Sunday completed the fourth day of a trek that is expected to take almost a month and represents by far his biggest challenge to the Turkish strongman since he took over the CHP in 2010.
But Erdogan the day earlier had said such actions bring no good for the country and bluntly told Kilicdaroglu "don't be surprised" if legal proceedings were opened.
"They want to provoke us but we will not give in! They want to threaten us with the courts and he (Erdogan) calls out the judges, the prosecutors," said the CHP chief.
"We are walking for justice, not against justice," he added, quoted by the party while the march.
Kilicdaroglu, 68, has made the word "justice" the slogan of his march, clutching a stick with the word emblazoned on a card.
His plan is for the 450-kilometre (280 miles) trek to culminate at Maltepe prison in Istanbul where Berberoglu is being held.
Political tensions have been rising in Turkey after Erdogan on April 16 narrowly won a referendum granting him greater powers that the CHP fears will lead to one-man rule.
Kilicdaroglu accused Erdogan of being the "July 20 coup plotter" over the crackdown that followed the failed July 15 putsch to oust him from power.
Erdogan on July 20 declared a state of emergency that has seen some 50,000 people arrested and another 100,000 lose their jobs in the biggest purge in modern Turkey's history.
Kilicdaroglu invited Erdogan to spend "a night in the caravan" on the way, sarcastically warning the president: "We don't have golden toilets in the caravan."
The CHP leader had accused Erdogan of having golden toilet seats in his palace, an accusation the presidency denied.
"I want to remind you -- there is a Moses for every pharaoh. Don't forget this," he said, referring to the Israelite prophet who led the exodus from Egypt.