Opposition All People’s Congress (APC) presidential candidate Samura Kamara said on Twitter that live bullets had also been fired at his office inside the party headquarters in the capital Freetown.
Sidie Yahya Tunis, a spokesman for the APC, told AFP that one woman had died in the incident.
“She was downstairs in the medical unit — she’s a nurse — we have a little health clinic in our office, that’s where she was working,” he said.
Yvonne Aki-Sawyerr, a prominent APC member bidding for a second term as Freetown mayor, tweeted photos from inside the building showing people taking cover on the floor.
“I am in the APC Party office and we are under fire,” she wrote.
In a statement, the Sierra Leone Police said that members of the APC had paraded through Freetown “announcing to the public that they had won” the elections.
They attracted “a huge crowd” of supporters outside the headquarters, who “started harassing passers-by”, the force said.
“When the situation became unbearable, the Police had to fire teargas canisters so as to disperse the crowd which was harassing people on the road,” it added.
Vote tallying got underway across the country earlier on Sunday, but results have not yet been announced.
Voting during Saturday’s presidential, parliamentary and municipal elections was mostly peaceful.
But on Sunday, chief electoral commissioner Mohamed Konneh outlined a number of districts where he said polling staff had been attacked by members of the public.
Also on Sunday, the Sierra Leone People’s Party (SLPP) of President Julius Maada Bio alleged in a statement that “top-ranking members” of the APC had attacked its polling agents.
On Saturday evening, senior members of the opposition party told AFP that violence had taken place near several polling centres in Freetown.
The head of the Office of National Security, Abdulai Caulker, said at a press conference that he was not aware of those alleged incidents.
Clashes also broke out outside APC’s headquarters on Wednesday after the party called for “peaceful” nationwide protests.
Sixty-six people were arrested Wednesday across Freetown, police said.
The APC has also alleged that its supporters were attacked while campaigning in rural parts of the country.
Some level of political violence is typical of Sierra Leonean election campaigns.
– ‘Concerned’ –
On Sunday evening, the European Union Election Observation Mission said it was “concerned about the ongoing tabulation process”.
“Considering the highly polarised political environment and prevailing mistrust, it is imperative that the Electoral Commission for Sierra Leone provides full transparency during the tabulation of results,” chief observer Evin Incir said in a statement.
The Carter Center, which also sent an observation mission, said Sunday evening it was concerned “about reports indicating a lack of transparency during parts of the tabulation process”.
Kamara of the APC alleged in a statement earlier on Sunday that the electoral commission was making it “impossible for us and other political parties to compare, reconcile and verify” tallying.
The APC has for weeks accused the electoral commission of bias in favour of the governing party, raising speculation that it is laying the groundwork for a court challenge of the results -– a tactic both parties have used in the past.
Konneh of the electoral commission said in a press conference that the party’s demands were “practically impossible” given the scale of the tallying.
Many polling stations opened and closed late in Freetown on Saturday, with voting officially ending at 11:30 pm (2330 GMT), according to Konneh.
He said it had been “one of the best election days” in recent history, “if not the best”.
Results are expected within 48 hours of the vote.
– Key players –
Twelve men and one woman were running for president, but incumbent Bio’s main challenger is Kamara of the APC. Bio narrowly beat Kamara in a runoff in 2018.
Both main parties said they were confident of victory in statements on Sunday.
Some 3.4 million people were registered to vote, the electoral commission said.
Presidential candidates must secure 55 percent of valid votes for a first-round win.
Turnout has ranged from 76 to 87 percent over the past three elections.
Voters will also elect members of parliament and local councils under a new proportional representation.
A June 14 poll by survey group Institute for Governance Reform forecast that Bio would win 56 percent of the vote, with 43 percent for Kamara.
Another poll, conducted by the newspaper Sierra Eye and two local data groups, forecast 38 percent for the incumbent and 25 percent for his main challenger.
The elections are being closely followed in West Africa, a region recently dominated by coups and turmoil.