Protesters berated Nicaragua’s president, Daniel Ortega, on Wednesday and demanded his removal at the start of “peace” talks designed to defuse weeks of unrest and deadly repression in which scores have been killed.

Critics chanted “Asesino!” or “Killer!” as Ortega and his vice-president and first lady, Rosario Murillo, arrived at a seminary in the capital, Managua, for the talks, which come nearly a month after public rage over social security reforms erupted into the biggest political challenge to the former Marxist revolutionary since his return to power in 2007.

Initial demonstrations over that unpopular move swelled into a broader nationwide revolt against Ortega’s 11-year rule after they were met with lethal repression by pro-government forces. According to human rights groups, at least 65 people, many of them student protesters, have been killed so far.

In an editorial marking the start of Wednesday’s talks, the opposition broadsheet La Prensa urged Ortega’s critics to give the dialogue a chance, despite fears the “cunning and unscrupulous” politician would outwit them. It called on opposition representatives to demand an immediate suspension of government repression and a commitment that no more students would be killed.

“The dialogue must focus on the two key points which are: achieving justice for those who were massacred … and agreeing to a plan and a roadmap for the process of Nicaragua’s democratization,” La Prensa said.

There were angry scenes as the dialogue began at about 10am on Wednesday.

“You can sleep easily. Not us. We are being persecuted,” one student leader, Lester Aleman, shouted at Ortega during the talks, which are being mediated by the Catholic church.

The student added: “We’re not here to hold a dialogue. We are here to negotiate your departure.”

According to one local journalist, Murillo, the focus of much of the public anger, reportedly told the students: “We all feel anger over what happened in Nicaragua but the path forwards is not war.”

Student representative Lester Aleman interrupts Nicaragua’s President Daniel Ortega, shouting that he must halt the repression, during the opening of the national dialogue. Photograph: Alfredo Zuniga/AP

Protesters – many of whom are now adamant that their Sandinista president must go – said they were doubtful the dialogue would bring any lasting solution.

“People now want him out,” said Xilonem Vargas, a 27-year-old protester from Masaya, a city to the south-east of Managua that suffered some of the most recent deadly violence on Saturday.

“[When the protests began] you used to hear chants saying: ‘Justicia! Justicia!’ or ‘They were students, not delinquents’,” Vargas said.

“Now the main chants are: ‘Let’s get Daniel Ortega out! There is no other option. We cannot dialogue with a murderer.’

“We just don’t know what is going to happen. Everyone is acting very unpredictably,” Vargas added.

Istvan Sepúlveda, a 31-year-old protester from the western city of León, said he welcomed the prospect of a “ceasefire” but feared the talks would make it easier for the government to paint those who continued to take to the streets as troublemakers.

Demonstrators walk past graffiti reading ‘Murderous Police’ during a protest against President Daniel Ortega’s government in Managua on Tuesday. Photograph: Oswaldo Rivas/Reuters

“I believe it’s a first step. It’s necessary … [But] I think the dialogue is more a facade to present to the international media.”

Unlike many members of the student-led protests, Sepúlveda said he was not convinced the immediate exit of Ortega and Murillo, was a good idea. “If they leave there is going to be a power vacuum and that could be even worse.”

However, he said Ortega needed to offer genuine concessions this week, including justice for those slain by security forces and a commitment to transparent and democratic elections in the future.

“If not, I think the protests will continue and might even intensify … It’s been like a pressure cooker and now it has reached boiling point,” Sepúlveda added.