President Uribe looks set for four more years

Colombians go to the polls on 28 May to elect a president and vice-president to a four-year term that will begin on 7 August.

Six candidates are standing but the incumbent president, Alvaro Uribe, has a commanding lead in the opinion polls and is expected to win a majority in the first round, effectively bucking the trend in Latin America towards left-wing governments.

A recent change to the constitution has allowed Mr Uribe to stand for a second term, the first time in more than 100 years a Colombian president has been allowed to stand for immediate re-election.

What are the main issues?

Armed conflict: There is still no end in sight for the 40-year war against the main guerrilla groups, the Revolutionary Armed Forces of Colombia (Farc) and the smaller National Liberation Army (ELN).

The government has held preliminary peace meetings with the ELN but has taken a hard line on a Farc proposal for a humanitarian swap of prisoners for hostages.

Paramilitaries: Uribe's greatest success has been the successful demobilisation of about 26,000 paramilitaries belonging to the Colombian United Self-Defence Groups (AUC).

Critics have expressed fears that the demobilization process will allow paramilitary leaders to escape lengthy jail sentences for drug-trafficking, murders and human rights abuses. A recent UN report found that some paramilitary groups were regrouping.

Crime: Colombia is still the world's main producer of cocaine despite the government's efforts to eradicate drug crops, boosted by more than $3bn in aid from the US through Plan Colombia.

Refugees: A report by the United Nations High Commissioner for Refugees in April 2006 stated that over two million people have fled their homes because of the conflict, a refugee situation second only to Sudan.

Economy: Unemployment is one major issue - official figures put it at around 13% - and all candidates recognise the need to give priority to job creation schemes. There is less agreement on a proposed free trade agreement with the US, with some candidates in favour and other vehemently opposed.

What is the voting system?

To be elected president in the first round, a candidate must obtain over 50% of the votes cast.

If no candidate obtains sufficient votes to win outright, a second-round runoff will be held between the two top candidates on 18 June.

Who can vote?

All Colombians over the age of 18 are eligible to vote. Out of a population of 45.6 million, there are over 26.7 million registered voters.

More than 10,000 voting centres will be set up around the country. Colombians abroad and registered to vote will be able to cast their ballots at consulates in 52 countries.

The polls are scheduled to open at 0800 (1300 GMT) and will close at 1600 (2100 GMT).

What is the security situation?

The election comes against a background of recent violence, including the murder on 27 April of Liliana Gaviria, the sister of former President Cesar Gaviria, the head of the Liberal Party.

A few days before the election, an additional 1,200 army troops will be brought in to control routes into the capital, Bogota, and 600 members of a special anti-terrorist squad will monitor 14 key points in the city, according to the police chief. A total of 220,000 members of the security forces will be deployed throughout the country.

In an unusual move, the Farc guerrillas have said they will not disrupt the elections. Instead they called on Colombians to vote against the "fascist, paramilitary president".

However, the government has said it expects an increase in attacks leading up to 27 May, the date the Farc marks as its foundation in 1964.

What happened at the last election?

Mr Uribe's first-round victory over Liberal Party candidate Horacio Serpa in the 2002 presidential election changed the whole structure of Colombian politics, breaking the traditional hold on power that the Liberal and Conservative parties had exercised since the 19th century.

A dissident Liberal, Mr Uribe stood as an independent, winning the election on a strong anti-guerrilla, anti-crime, pro-US platform which appealed to Conservative voters.

He was also able to appeal to a significant number of traditional Liberal voters, effectively splintering the Liberal Party.

Who are the main candidates?

Alvaro Uribe Velez: The 54-year-old president is a tough-talking, no-nonsense former mayor of Medellin, who has made security the main focus of his campaign.

His father, a wealthy landowner, was murdered in a botched kidnap attempt by the Farc in 1983, and he says he needs four more years to consolidate security, eradicate poverty and eliminate corruption.

His simple message has hit a nerve with Colombians, despite a slew of allegations of links between government officials and paramilitary groups.

Horacio Serpa Uribe: This is the third time the 62-year-old Liberal stalwart has stood for president but he has found it hard to rally support for his campaign.

He has consistently denounced the growth of the paramilitaries under the Uribe presidency and has proposed housing and job creation schemes to tackle widespread poverty in rural areas.

Despite losing ground in the polls, he predicts he will beat Mr Uribe in a runoff election.

Carlos Gaviria Diaz: Mr Gaviria, 69, is a Harvard-educated lawyer and former High Court judge, who is standing for a left-wing coalition ranging from moderates to communists.

An admirer of Venezuelan President Hugo Chavez, Mr Gaviria has pledged to nationalise strategic industries and opposes a free trade agreement with the US. He also favours peace talks with the country's rebel groups.

Who is likely to win?

According to a poll, published by the daily newspaper El Tiempo on 21 May, Mr Uribe is leading the field with 55%, Mr Gaviria is in second place with 23.7% and Mr Serpa trails with 10%.

Although voting is compulsory, abstention at the 2002 presidential election was 54% and a similar or larger figure is expected this time.

Mr Uribe's campaign team fear that the president's strong showing in the polls could work against him on election day as, confident of victory, his supporters might stay away.

BBC Monitoring selects and translates news from radio, television, press, news agencies and the internet from 150 countries in more than 70 languages. It is based in Caversham, UK, and has several bureaux abroad.