Colombians voted in congressional polls that are likely to determine who will succeed the outgoing president after May's presidential election.

Voters cast their ballots on Saturday as all land borders were closed to ensure what the interior ministry called "the normal activities of the electoral voting".

Keeping a majority

The coalition of Uribe's Conservative party and its allies is likely to keep its majority in both chambers of congress, despite 12 pro-Uribe legislators being convicted on charges linked to rightist paramilitary death squads.

After two terms in office - ending in August - Uribe's nurturing of the economy to its best performance in 30 years and his crackdown on the Revolutionary Armed Forces of Colombia (Farc), have earned him a near 70 per cent popularity rating.

But the congress is not nearly as popular: aside from the 12 convicted, at least 80 legislators are under investigation for alleged links to paramilitary groups.

One political party was struck from the voting list on suspicion its leaders had links to paramilitaries, though opposition groups claim the party simply renamed itself and kept the same people, or their relatives, in charge.

Al Jazeera's Teresa Bo, reporting from a polling station in Corinto, said there had been reports of intimidation by a paramilitary group on the election day.

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"[Reports] are suggesting that paramilitaries have been forcing people, especially in rural areas, by telling them which candidate they have to go for," she said.

"Let us not forget that many paramilitary groups are trying to get candidates into congress."

The Organisation of American States (OAS) cautioned that drug cartels could influence the elections with their mountains of cash.

A senior OAS official told El Tiempo daily: "We've heard many voices and all seem to concur that still there are criminal groups - not just the paramilitaries - directly linked to drug trafficking that are trying to have a perverse influence in politics.”

Enrique Correa, chief of the OAS election observer mission, said in an interview published on Saturday: "In Colombia there is still a risk drug trafficking will try to influence politics, as it does in the entire world."

Presidential pick

About 150,000 military and police fanned out across Colombia to safeguard some 77,000 polling stations.

About 29.8 million Colombians were registered to vote to choose from 2,539 candidates to fill congress' combined 268 seats.

Five members will also be elected to the regional Andean Parliament.

Sunday's vote also kicked off internal consultations in the major Conservative and Green parties to pick a candidate for the May 30 presidential election, with a runoff, if needed, on June 20.

Uribe's absence from the presidential race - his bid for a third term in office was blocked last month when the constitutional court ruled a referendum on the issue unconstitutional - has left his supporters without a clear leader.

Among the half-dozen Conservative members vying to be the candidate, two are most likely to succeed: Noemi Sanin, Uribe's former ambassador to Britain, and Andres Felipe Arias, an ex-agriculture minister.

Uribe's conservative administration is Washington's principal ally in South America both in the fight against regional drug trafficking and in trying to counter the growing influence of Hugo Chavez, the Venezuelan president.