Urban peace demonstrators marked the police killing last week of a 10-year-old boy in Rio de Janeiro with a parade along the seafront on Sunday, bearing a coffin, a black cross and the names of more than a dozen other child victims.

The symbolic protest in Copacabana followed the biggest rally against police violence in four years, which was sparked by a deadly escalation of conflict between public security forces and gangsters in the troubled Complexo de Alemão favela community.

The killings and street protests highlight the growing challenges facing Rio’s ambitious program to “pacify” several-dozen slums – a key element in the city’s efforts to improve public security ahead of the 2016 Olympics.

The Complexo de Alemao, long a stronghold of the Comando Vermelho (Red Command) gang, has seen a sharp increase in violence in recent months, with shootings every day this year. Police and alleged gangsters have been killed, along with innocent bystanders.

Last week saw the death of 10-year-old Eduardo Ferreira, who was shot by police, apparently because they thought the cellphone he was taking out of his pocket was a gun. Officers were more nervous than usual because several of their colleagues have been killed in the area in the past weeks.

A crowd of about a thousand people marched through Alemão this weekend in the biggest protest the community has seen since the start of its pacification operation four years ago. The dead boy’s mother, Terezinha Maria de Jesus, screamed at police who were watching the protest: “Assassins. You murdered my son, you cowards.”

Other demonstrators bore banners reading “Peace in the Favelas”, “Less Bullets. More Love” and “Je Suis Eduardo”.

At Sunday’s march, Antonio Carlos Costa, the founder of the Rio de Paz (Rio of Peace) NGO, said more than half a million people had been murdered in Brazil in the past 10 years, at least 80% of them from poor communities like Alemão.

Recognising that many of the police victims were also from favelas, he called on the authorities to invest in education and poverty relief programs to address the root causes of the violence, rather than putting more money into the militarisation of public security.

“The violence of Rio is an attack on our children,” he said to journalists and fellow protesters who were dressed in black mourning clothes.

Others said the demonstration was not aimed at the police.

“The police are not the enemy,” said one of the demonstrators, Manuela Cantalice. “Although they kill many people. Many police are also killed. What we need [is] a debate about police behaviour and training.

“We cannot stand by and watch as our kids die without the protection of society. People in the slums should not be treated like the outcasts of society.”