The two marches in Managua came after protests and looting last week that Nicaragua's Permanent Commission on Human Rights said left at least 63 people dead, 15 missing and more than 160 wounded by gunfire.
The government of President Daniel Ortega has not confirmed or denied the casualty figures.
Mr Ortega, who began his third five-year term in office last year, withdrew the social security overhaul that sparked the social convulsion last Sunday and agreed to meet with different sectors of society.
The rescinded changes would have imposed higher contributions by workers and employers and required retirees with pensions to give up 5% of their checks for medical care.
But the protests, which have been largely led by university students, had expanded beyond the original opposition to the social security changes to include broader anti-government grievances. Protesters at times were met with violent with police repression and attacks from Sandinista youth and motorcycle-riding thugs.
On Monday, Nicaragua's private business sector organised a march calling social peace and an end to repression that drew tens of thousands of participants, marking the largest demonstration seen against Ortega's Sandinista government.
Saturday's march called by the Episcopal Conference of Nicaragua also drew tens of thousands of participants, including students, representatives of the private sector and opponents of the construction of an interoceanic canal.
"We are going to march for peace so that there is justice. We Nicaraguans need a better country and we will achieve it," Silvio Baez, auxiliary bishop of the archdiocese of Managua, told local media.
Today's giant march in Nicaragua pic.twitter.com/l7n7NRZx4w
— JesseJT (@followthestorms) April 28, 2018
Francisca Ramirez, a leader of the anti-canal movement, said "it is time for Daniel Ortega to understand that he cannot continue doing whatever he wants with this country."
"It has been enough. We want peace but with justice for the murders," Ms Ramirez added.
On Friday, National Assembly president Gustavo Porras announced the creation of a truth commission to look into the deaths and what happened in the protests and clashes, which were seen by Nicaraguan analysts and historians as the most violent and bloody since the Somoza dictatorship.
Similar demonstrations were held on Saturday in other cities such as Matagalpa and Leon.
"I came because the young people who died deserve a tribute, that we march for the peace in the country, for justice and for the return of the democracy that has been kidnapped by this government," said Marlene Alvarez, 26, who works in a laboratory in the capital.
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