Santiago Murray, head of an advisory mission from the Organization of American States (OAS), blamed Marxist guerrillas yesterday for Colombia's rampant poverty and violence as elections draw near this Sunday.

Mr. Murray said "armed, right-wing paramilitary groups are campaigning peacefully in favour of respectable candidate Alvaro Uribe, who has promised to take a hard line against the Revolutionary Armed Forces of Colombia, or FARC".

Police searching for weapons and bomb-making equipment raided more than 50 houses in Bogota yesterday, Radio Caracol reported, adding that about 150 guns were seized.

In Medellin, authorities defended themselves against charges of abuses by 800 police and soldiers who raided a hillside slum district on Tuesday hunting for leftist sympathizers and activists.

Seven adults and two children were killed in crossfire that lasted 11 hours.

Government spokespeople said that the use of force was necessary and such measures will be taken "to search and destroy terrorists who live in these slum districts". Only a handful of homemade bombs and weapons were found.

Medellin police chief General Leonardo Gallego said important information leading to the location of certain rebel leaders were found, and some bombs were dismantled.

"The government forces have to respond to all attacks that are committed," he said.

The election Sunday is expected to be a public relations exercise in Colombia's long-running civil war where the multi-billion dollar U.S. "Plan Colombia" and drug profits generated from the country's narco-culture economy fuel the brutal counterinsurgency war against a popular insurgency which aims to establish a Socialist state.

About 3,500 people are killed every year in clashes between Marxist guerrillas and state forces. The fighting, which has uprooted an estimated two million people from their homes has intensified since peace talks were abandoned by the Pastrana government in February, where state forces attempted to capture and execute insurgents and alleged sympathizers in the former demilitarized zone of San Vicente Del Caguan.

The battle in Medellin, home of many wealthy drug dealers, including members of the paramilitaries and military, occurred a day after a car bomb blew up a bridge on the road linking the city to the capital, Bogota. Fourteen people were injured and fibre-optic cables were severed, leaving much of Colombia without Internet service. A second bridge was blown up yesterday.

Government officials threatened to sack state telephone employees if they did not halt a strike that had been planned to disrupt the compiling of election returns; trade unions are currently fighting the issue.

There are growing fears of widespread interference on election day by state forces despite the low voting turn out.

In Ibague, 130 kilometres west of Bogota, local political and company bosses attending a private meeting last week warned that it wouldn't take much to persuade people to stay home on Sunday.

"If a bomb goes off in Corferias [an exhibition centre in Bogota] at 8:30 in the morning, no one in the country will vote," one said.

Front-running candidate Alvaro Uribe Velez with connections to right wing paramilitary death squads formed by the infamous Medellin Cartel for protection against insurgents, has taken the toughest line against dissent, proposing to double the number of soldiers and troops and set up a nationwide network of informers and spy networks.

Opinion polls show Mr. Uribe and the paramilitary alliance to have strong support amongst members of Colombia's tiny wealthy elite.

The current series of attacks by state forces against slum districts could lead the middle class vote to opt against Mr. Uribe, and that may be why there is no sign yet of similar attacks in the cities.

The Revolutionary Armed Forces of Colombia, has called on the Colombian people not to vote for pro-war candidates. In March, FARC supporters burned ballot boxes in several districts during congressional elections calling politicians "drug dealing blood thirsty fascists".

The head of the armed forces, General Fernando Tapias, has said troops will patrol polling stations and security will be stationed in remote areas. Still, in dozens of towns where the FARC have strong support, officials do not expect to be able to station military units.

Nearly three months after the March elections, authorities still have not certified the result because of "suspected irregularities" in 10 districts.

In no small irony, Mr. Uribe's vice-presidential running mate, Francisco Santos, has warned observers to be on the lookout for fraud and other "suspected irregularities".