The West African country held presidential, parliamentary and local council elections on Wednesday, which passed off largely peacefully until an opposition leader's residence was raided.
The National Election Commission (NEC) has asked for patience as it counts the ballots, saying it will prioritise accuracy over speed.
It said on Friday it had yet to reach the 25 percent mark required to release provisional results.
However, the ruling All Peoples Congress (APC) said in a statement it had a "comfortable lead" over its rivals, causing the Sierra Leone People's Party (SLPP) to accuse them of "endangering public order and national security."
The SLPP claimed the APC was preparing to release "fake presidential results", adding that it remained "confident of a clear victory".
It comes after the opposition party's leader Julius Maada Bio's residence was raided by police on a bizarre "hacking" accusation despite Sierra Leone using a manual voting system.
'Transparent, credible'
Partial results are expected in the next few days but must be verified by the National Election Commission (NEC).
European Union (EU) observers meanwhile described the election as "transparent, credible and well-organised" in a statement on Friday.
However, they said police reaction during the Bio raid was "disproportionate", and called on the officers to exercise their duties in an "impartial, proportionate manner".
The EU added that an "increasing number of acts of intimidation and violence against candidates and activists affected the electoral process."
The Campaign for Human Rights and Development International (CHRDI), a Freetown-based organisation, went further and called police behaviour "unprofessional".
"They were seen brutally beating up protesters unnecessarily," the group said.
Clashes between rival supporters in Freetown also led to arrests on Wednesday.
The APC and SLPP have dominated Sierra Leone's politics since independence in 1961, but third parties are hoping to make their mark after mounting charismatic campaigns based on the two parties' shortcomings.
The National Grand Coalition (NGC), whose message of reform has struck a chord with educated urban voters, elsewhere said it had identified "a number of serious irregularities in the voting process which will in some areas require immediate recounts".
It would complain to the NEC, it added.
Sierra Leone's export-dependent economy of the mineral-rich but impoverished country is in a dire state following the 2014-16 Ebola crisis and a commodity price slump that has driven away foreign investors.
A presidential runoff is likely, according to experts, as the threshold to win outright in the first round is 55 percent.
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