ISTANBUL — Hundreds of thousands of protesters have arrived here in Istanbul in the culmination of a three-week March for Justice, delivering a powerful message of complaint against the government’s crackdown on tens of thousands of workers over the past year.

The march, which has been led by politicians from Turkey’s largest opposition party, the Republican People’s Party, known as CHP, has drawn growing numbers of people as they have trekked since June 15 through the countryside from the capital, Ankara, to Turkey’s first city, Istanbul.

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The marchers entered the outskirts of Istanbul on Saturday and will end their protest with a large-scale rally on the eastern side of the city on Sunday evening. Wearing T-shirts and carrying signs with the single word “adalet” or “justice,” the demonstrators are calling for the return of an independent judiciary and swift and fair justice for the tens of thousands of people arrested or suspended from their jobs since Turkey’s failed coup last year.

Despite their differences, however, the government and opposition leaders appeared to be taking great pains to prevent a major confrontation as the march reaches its culmination. The rally on Sunday will technically be in breach of the state of emergency that has been in force since the coup attempt. Large numbers of police officers have escorted the march but have not interfered.

In a symbolic gesture, but also perhaps in an effort to manage the crowds, the leader of the CHP, Kemal Kilicdaroglu, will walk the last two miles to the rally on his own. A former civil servant, Mr. Kilicdaroglu, 69, has captured the imagination of many supporters with his mild manner and his insistence on a peaceful march, in the spirit of Mahatma Gandhi.

“This is not an antigovernment protest,” Samet Akten, communications director for the march, said in a statement on Sunday.

“It is important to recognize the exceptionally peaceful nature of this process as well as its very specific goal,” he added. “We will be expressing a collective, nonpartisan desire for an independent and fair judicial system, which has lately been lacking in Turkey.”

Though the government has allowed the march and rally to go ahead despite security concerns and its evident criticism of President Recep Tayyip Erdogan’s authoritarian leadership, it is the largest sign of opposition to Mr. Erdogan since the failed coup last July, in which more than 200 people were killed

Politicians, including the CHP, rallied behind the president after the coup attempt, but differences have since emerged over the scale of his crackdown. Mr. Erdogan has arrested some 50,000 people accused of links to the coup plotters, and has held a referendum that granted him greater powers, including over the judiciary.

In an interview with the German daily Die Zeit last week, Mr. Erdogan insisted that the judiciary in Turkey was independent and defended the widespread arrests, saying many of those detained, including journalists, faced serious charges of terrorism.

“If it turns out that they are innocent, the judiciary will release them,” he said. “But if they are guilty, the judiciary will rule accordingly.”

CHP organizers have urged marchers to react calmly to any provocation from pro-government opponents. Leaders commended the police management of the crowd on Saturday as exemplary

As they completed the last miles into the city along the coastal highway, marchers rested under trees on the grassy sidewalks. They expressed hope for justice but also political change that would bring an end to arbitrary arrests and create equal access to jobs. The CHP is a secular party, and some female supporters said they wanted a reversal of the Islamist trend that has occurred under Mr. Erdogan.

Government supporters were largely absent. Some workers watched in silence. Drivers complained that roads were sealed off for the march.

“God sees everything,” one driver said.