* Largest protest against Turkey's post-coup crackdown
* Kilicdaroglu says march and rally are just "first step"
* Erdogan says protesters should seek justice in parliament (Recasts with speech)
By Umit Bektas and Humeyra Pamuk
ISTANBUL, July 9 (Reuters) - Turkey's main opposition leader told a huge protest rally on Sunday that the country was living under dictatorship and pledged to keep challenging the crackdown launched by the authorities after last year's failed military coup.
Addressing hundreds of thousands of people waving Turkish flags and banners demanding justice, Kemal Kilicdaroglu said his 25-day march from Ankara to Istanbul - culminating in Sunday's rally in Istanbul - was the first stage of a long campaign.
"We will be breaking down the walls of fear," he told the crowd who gathered to welcome him at the end of his 425 km (265 mile) trek from the Turkish capital.
Kilicdaroglu's protest march drew only modest support in its early days, but as more people joined him it grew into the biggest protest yet against the year-long, post-coup crackdown launched by President Tayyip Erdogan's ruling AK Party. "The last day of our Justice March is a new beginning, a new step," said Kilicdaroglu, a bespectacled, 68-year-old veteran politician. "Rights, law, justice," the crowd chanted back.
He called on the government to lift a state of emergency enforced after the abortive July 2016 coup, release scores of journalists from prison and restore the independence of Turkey's courts.
Kilicdaroglu, head of the secularist Republican People's Party (CHP), launched his protest last month after the jailing of a fellow parliamentarian for 25 years on spying charges.
Enis Berberoglu was the first CHP lawmaker to be imprisoned in the purge. About 50,000 people have been arrested and 150,000 state workers including teachers, judges and soldiers, have been suspended.
"The era we live in is a dictatorship," Kilicdaroglu said.
"AGAINST ONE-MAN RULE"
Rights groups and government critics say Turkey has been drifting toward authoritarianism for years, a process they say accelerated since the coup bid and a referendum in April which granted Erdogan stronger powers.
The government says the crackdown and constitutional changes are necessary to address challenges and security threats.
Erdogan criticised Kilicdaroglu when he launched his protest, saying justice should be sought in parliament, not on the street. He likened the protesters to those who carried out the attempted coup, saying they could face charges.
But Kilicdaroglu said the opposition had no alternative because Turkey's courts had been politicised, "the powers of parliament have been seized" and the media had been muzzled.