(BBC)- - Voting has opened for a new president of the Democratic Republic of Congo, in one of Africa's most significant elections for many years.
President Joseph Kabila, who came to power after his father Laurent was assassinated in 2001, is facing former rebel leader Jean-Pierre Bemba.
The UN-backed election is intended to crown a peace process that ended five bloody years of civil war in 2003.
Correspondents say the outcome could shape the future for much of Africa.
Sunday's run-off will conclude the DRC's first fully democratic polls since independence in 1960 and is aimed at restoring peace to one of Africa's largest and most turbulent states.
The BBC's Mark Doyle in Kinshasa says it is impossible to exaggerate how the destiny of DR Congo could shape the future of Africa.
Nine African states border the country and all were affected by the wars caused by the long lack of real government in DR Congo, the power vacuum at the heart of Africa, he says.
UN officials say the polls are the most important on the continent since the 1994 election of Nelson Mandela that ended apartheid in South Africa.
However, our correspondent says the candidates are not Nelson Mandelas and neither of them has a good record of being a democrat.
Mr Kabila has strong support in the east of Congo; Mr Bemba is popular in the west.
This political split across the geography of a vast nation is the same split that in the past led to a war in which four million people are estimated to have died, our correspondent adds.
'Tense but manageable'
Mr Kabila won first round polls on 30 July, but fell just short of the 50% needed for outright victory.
At least 23 were killed in armed clashes between the two men's security forces in Kinshasa after the results were announced.
United Nations Secretary General Kofi Annan has called on the two candidates to ensure that the election is peaceful. Both men have promised to urge their supporters against violence and to abide by election rules.
A UN official in Kinshasa has described the situation as "tense but manageable".
Extra UN peacekeeping troops are on standby in the east of the country. In the capital, Kinshasa, the UN is being backed up by a special European Union military force.
The United Arab Emirates acknowledged on Tuesday that two of its pilots were killed when their military aggression plane crashed over Jawf province, a military official said
The official added that the aggressive crashed plane was an apache that was
Artillery of the army and popular shelled a gathering of Saudi-paid mercenaries in al-Moqadra area in Serwah district of Marib province, a military official said on Tuesday.
Meanwhile, dozens of Saudi-paid mercenaries were killed and others injured in Wadi al-Theek in the district, the official added.
The army and popular forces carried out on Monday unique military operations in Taiz province.
A military official said that a number of Saudi-paid mercenaries were killed at the hands of the army and popular forces in al-Jazami Hill in al-Kadaha area in al-Ma'afer district.
A Saudi aggression fighter jet targeted a citizen's car driving in Fara area of Kutaf district in Saada province overnight, killing the driver and injuring his friend, a security official said on Monday.
The army artillery and popular committees launched a fierce attack on Saudi-paid mercenaries' sites in Jawf province, a military official said on Monday.
The attack destroyed a military vehicle belonging to the mercenaries and killed all on board in Sabran area in khab and shaaf district.
Scores of Saudi enemy soldiers were killed and injured on Sunday when the army and popular forces repelled a Saudi military attempt to sneak into Shurfah site in the border province of Najran, a military official said.
The operation was accomplished successfully against the Saudi
The army and popular committees have killed a total of 18 Saudi-paid mercenaries in sniper operations over the past hours in the central province of Marib, a military official said on Sunday.
Ten mercenaries were killed in Nehm district and eight others were killed in Serwah district, said the official.
Saudi aggression warplanes have launched more than 49 airstrikes over the past hours on several residential areas across Yemen, a security official said on Sunday.
The airstrikes targeted the areas of Malahiz and Husama in Dhahir district, and areas Thuban, Masahif and Sdad in Bakim district of northern Saada province.