Republican People's Party (CHP) leader Kemal Kilicdaroglu challenges President Recep Tayyip Erdogan to resign

Turkey's main opposition Republican People's Party leader Kemal Kilicdaroglu gives his weekly speech in the town of Camlidere in the Ankara Province, on June 20, 2017. (Photo by AFP)

Turkey's main opposition leader has challenged President Recep Tayyip Erdogan to resign if it is proven that the government influenced the judiciary in the post-coup crackdown in the country.

Republican People's Party (CHP) leader Kemal Kilicdaroglu made the remarks in a Tuesday speech for hundreds in the town of Camlidere on the outskirts of Ankara on the sixth day of his "walk for justice" protest march from Ankara to Istanbul.

"If I prove you and your government gave instructions to the courts, will you resign from your role as an honest and honorable person?" he said.

"I give my word as well. I will leave politics if I do not prove (these claims). Because I am an honest and honorable person,” he added.

The 68-year-old Kilicdaroglu leads the march in protest at a heavy jail sentence handed down to former journalist turned CHP lawmaker Enis Berberoglu.

A court sentenced Berberoglu to 25 years in jail on Wednesday for leaking classified information to a newspaper.

The 450-kilometer (280 miles) trek is expected to take almost a month and will culminate at Maltepe prison in Istanbul where Berberoglu is being held. The march represents Kilicdaroglu’s biggest challenge to Erdogan since he took over the CHP in 2010.

Turkey's main opposition Republican People's Party (CHP) leader Kemal Kilicdaroglu (C with white cap) participates in the "walk for justice" from Ankara to Istanbul against the government in the town of Saray north of Ankara on June 20, 2017. (Photo by AFP)

Kilicdaroglu said he was "walking for everyone who seeks justice," vowing, "We are a party who will defend democracy until the end."

The opposition accuses Erdogan of shifting towards authoritarianism, especially since last year's failed coup which was followed by a massive crackdown and the April referendum which expands the president’s power.

Kilicdaroglu calls Erdogan the "July 20 coup plotter", referring to the date when the president declared a state of emergency.

Erdogan said Saturday that actions like the march by Kilicdaroglu would bring no good for Turkey, saying the opposition leader should not "be surprised" if legal proceedings were opened.

Kilicdaroglu said he was undeterred by Erdogan’s threats that the action might lead to legal proceedings against him.

Turkey has seen a surge in political fighting since a failed coup attempt on July 15 last year. The opposition has constantly criticized a crackdown launched since the coup which has seen more than 40,000 people arrested and over 100,000 discharged from their jobs. Kilicdaroglu even once accused Erdogan of being the "July 20 coup plotter", saying he had used the deadly coup by military renegades to consolidate his rule in Turkey.

Tensions rose again on April 16 when voters endorsed changes to Turkey’s constitution and gave Erdogan more powers as president. The CHP has censured Erdogan’s narrow victory in the referendum while warning that Erdogan would slide Turkey into a one-man rule system.