The government had earlier put the death toll for the August 14 mudslide at 450 dead, while rescuers and aid groups warned that many of the more than 600 people missing would likely not survive.
"Over 1,000 perished in the mudslide and flood disaster, and we will never know the exact number now," Elenoroh Jokomie Metzger, the head of the women of Regent, said on Sunday during services honoring the disaster's victims, AP reported.
Regent is an area on the outskirts of Freetown where the mudslide hit.
Hundreds of burials have taken place, while rescue and recovery efforts have continued through rain that could bring fresh tragedy due to unsafe housing conditions.
Reverend Bishop Emeritus Arnold Temple, who delivered the Sunday sermon at a Methodist church near Regent, said an accurate count was important for accountability.
"It may well be over 1,000 Sierra Leoneans we are mourning now. But why should about 1,000 of our compatriots' lives end tragically like this?" Temple said.
"Who should we really blame? We are bound at a point in the blame game to attribute the blame so that corrective measures can be put in place so that never again should we allow this to happen."
First lady Sia Koroma, wife of President Ernest Bai Koroma, also spoke during the ceremonies.
"I stand here with a heavy heart. We have been through many calamities in our country," she said.
"We should all do self-examination and learn to be obedient to man-made laws, especially when the government plans to take action for the development of the country."
Thousands of people living in areas at risk during heavy rains have been evacuated. Aid groups are delivering supplies and helping provide clean water to prevent a health crisis.
Some critics accuse Sierra Leone's government of failing to learn from past disasters in Freetown, where many poor areas are near sea level and lack good drainage. The capital is also plagued by unregulated construction on its hillsides.