Colombian President Alvaro Uribe has defied rebel threats and gone ahead with a visit to the south-western town of Neiva a day after 17 people died in an explosion there.

The blast destroyed a house under the flight-path to the airport as it was being searched by police who had received a tip-off linking it to a plot to bring down the president's plane.

It's a provocation for the guerrillas, and we're the ones who will pay Alfredo Vargas, Neiva resident speaking of the president's visit

The BBC's correspondent in Colombia, Jeremy McDermott, says it now appears the tip-off came from Marxist guerrillas who planted explosives in the house which were detonated when the police broke in.

Meanwhile troops are combing the jungles of southern Colombia searching for three Americans who were kidnapped, reportedly by rebels from the Revolutionary Armed Forces of Colombia (FARC), after their plane crash landed on Thursday.

Rebels not intimidated

In Neiva Mr Uribe met the families of those killed in the bomb at a funeral home and visited the 30 injured survivors at a local hospital.

Mr Uribe's tough stance against the rebels is not working

The authorities have blamed the explosion on FARC guerrillas who have stepped up their campaign of violence in response to the president's get-tough policy towards the rebels.

Mr Uribe, who has already survived more than half a dozen assassination attempts in his political career has vowed to crush the rebels.

Our correspondent says the president is talking and acting tough, but the guerrillas are not intimidated and, instead, are themselves acting tougher than ever, no matter what the cost in civilian lives.

Last week 35 people were killed by a bomb in the capital, Bogota.

Search for hostages

Some of the people near the scene of the bomb blast in Neiva fear the president's presence could make matters worse.

"It's a provocation for the guerrillas, and we're the ones who will pay," said Alfredo Vargas, a teacher whose home was damaged in the explosion.

The search for the US hostages is underway

Mr Uribe has the backing of the United States. Three of its citizens, believed to be contractors working for the CIA, are now in guerrilla hands after their plane came down in the south of the country.

The four Americans and one Colombian on board were all reportedly alive when their single-engine Cessna crashed in the jungles of Caqueta province.

FARC rebels reached the survivors before local army units could find the plane, and killed one American and the Colombian "execution-style, in cold blood", according to General Jorge Enrique Mora, Colombia's senior military commander.

A massive search is now underway to locate the remaining three hostages.

General Mora said that helicopters, reconnaissance planes and special forces troops were all being used in the search.

"We have nothing new, and (the US nationals) have not been found. An intensive operation is under way. The objective is to find the three men," he added.