At least three killed in largest anti-government demonstration in decades demanding President Daniel Ortega to resign.

Hundreds of thousands of people took to the streets of Nicaragua’s capital calling on President Daniel Ortega to resign in the latest and largest anti-government protest in decades.

The Mother’s Day march in Managua on Wednesday was organised in solidarity with the mothers of students and peaceful demonstrators who have been killed by police and pro-government forces since the start of a nationwide political crisis on April 18.

At least three more protesters were killed, and several others wounded as anti-Ortega demonstrations continued and anger grew in the Latin American nation.

Just before sundown, masked gunmen opened fire on a group of demonstrators at the National University of Engineering.

Dozens of people, including women, children and students, took shelter for several hours in the Central American University campus because of the attacks, rights group Amnesty International said.

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With the latest fatalities, the number of people killed since the start of the unrest has climbed to at least 87, according to activists. Almost 900 have been wounded.

Crackdown on protesters

Over the past month, there has been rising unrest across the country after peaceful protests against reforms of the national pension plan were met with deadly force by the government.

Amnesty has accused the government of using a “lethal policy of state repression” and called for an immediate end to the violence.

“The government of President Daniel Ortega has reached inconceivable levels of perversion today,” said Erika Guevara-Rosas, the group’s Americas director, on the latest violence.

Ortega, a former left-wing rebel, fought to overthrow the US-backed Somoza dictatorship in 1979.

He has accused US-backed right-wing factions of steering the protests to destabilise his government.

“The violence is the worst this country has seen since the overthrow of Somoza’s dictatorship 40 years ago, and with the continued crackdown against peaceful protests, demonstrations with thousands of people marching on the streets of Managua have only grown,” said Al Jazeera’s Manuel Rapalo, reporting from Managua.

We want this government to have a conscience and stop killing our youth. Salanereyda Urbina Membreno, victim's mother

At Wednesday’s rally, mothers demanded justice for the killing of their children.

Salaneredya Ubina Membreno lost her 24-year-old son, Jeisson, who was shot and beaten to death during a student-led protest.

“We want this government to have a conscience and stop killing our youth,” she told Al Jazeera. “He was my only son … that’s why I want justice.”