|Al Jazeera's Yvonne Ndege reports from Monrovia on the violence during the run-up to the presidential run-off
Around 4,500 polling stations have opened in Liberia's presidential run-off election amid fears of violence and intimidation after clashes left at least four people dead in the capital, Monrovia.
Al Jazeera's correspondent Yvonne Ndege, reporting from Monrovia, said on Tuesday that the quiet atmosphere around the polling stations "might be one of the side effects of the violence and chaos around the streets of Monrovia yesterday.
"There is a sense that people are afraid to come out and vote [and] this could naturally have an impact on turnout.
"The opposition is calling for protests today and asking their supporters to wear black, and are calling today a funeral for democracy in Liberia." our correspondent said.
Meanwhile human rights group Amnesty International (AI) on Tuesday urged "police and all Liberian political candidates to act to stop the election related violence and prevent further bloodshed" and recommended an independent and impartial investigation into possible human rights abuses during the election period.
Carolyn Norris, Amnesty International’s deputy director for Africa, said in a press statement that politicians and police need to demonstrate that their main concern is protecting lives" after deadly clashes erupted between police and opposition supporters on Monday.
Demonstrators had taken to the streets after Winston Tubman, the opposition candidate hoping to unseat Ellen Johnson Sirleaf, said he would boycott the run-off and called on his supporters to do likewise over fears of fraud favouring the incumbent president.
'Case of sour grapes'
"Observers from ECOWAS, the African Union , European Union, and the Carter Center say that opposition's claims of fraud and electoral irregularity 'are a case of sour grapes."
- Yvonne Ndege
Tubman cried foul after being placed second in October's first round of voting, which he charged were riddled with irregularities in favour of Sirleaf.
But local and international observers have not found any evidence to support Tubman's allegations and his call for a boycott has drawn wide international condemnation, and drew a warning from Barack Obama, the US president, to unnamed individuals not to "disrupt the political process" in a nation still recovering from civil war.
"Observers from ECOWAS, the African Union , European Union, and the Carter Center say that opposition's claims of fraud and electoral irregularity 'are a case of sour grapes'," our correspondent Ndege said.
Shooting erupted on Monday as tensions soared between anti-riot police, UN peacekeepers and thousands of protesters gathering for an unauthorised march called by Tubman a day after the official end of campaigning.
Several schools which had served as polling stations in the first round where closed, fearing a repeat of Monday's violence.
"Some school buildings have denied us access to their premises. We are still negotiating with them to see if they will allow us," Elizabeth Nelson, National Elections Commission chairwoman, told the UN Mission in Liberia (UNMIL)
"Because of the incident yesterday all the voting centres did not open on time."
UN peacekeepers deployed
Several hundred people gathered at Tubman's Congress for Democratic Change headquarters on Tuesday morning, some having spent the night there.
Following the clashes on Monday, members of Liberia's UN peacekeeping force (UNMIL) had been deployed to intervene to break-up the clashes.
"Opposition supporters took me into their HQ and showed me three dead bodies of young men that they allege were shot indiscriminately by the Liberian police for simply protesting about the decision to continue with tomorrow's presidential election.
"It's an extremely bloody scene. It's so bloody, in fact, that the United Nations has sent tanks down here and peacekeepers to try and stop the confrontation between the police and those protesters," our correspondent Ndege said.
The Reuters news agency reported that Liberian police stormed the opposition party headquarters before being repelled by UN peacekeepers, who had set up a cordon around the building.
The report said that Liberian police fired tear gas and some live rounds as they entered the compound but were pushed back by Nigerian UN peacekeepers who were positioned there.
Yasmina Bouziane, a spokesperson for the UN mission in Liberia, did not confirm or deny the report.
"The people on the ground there did what they needed to do in order to bring the situation back down to order," she told Al Jazeera.
The election is Liberia's first locally organised presidential poll since the end of the 1989-2003 conflict that killed nearly a quarter of a million people.
Sirleaf became Africa's first freely elected female head of state in a 2005 election that was organised by the UN.