The attack came despote a military offensive that has dealt major blows to the FARC in the past several years

Colombian anti-government fighters have attacked a radar installation in Cauca province, killing a guard and delaying flights in the south of the Andean nation as well as some bound for neighbouring Ecuador and Panama, according to officials.

Members of the Revolutionary Armed Forces of Colombia, or FARC, launched homemade missiles and gas cylinders at the installation on Saturday, officials of the South American country's civil aviation authority said.

Juan Manuel Santos, the Colombian president, condemned the attack, saying: "When a group like the FARC attacks sites that cause problems for the civilian population, it's a demonstration of its weakness and desperation because it's affecting the civilian population that it claims to be its base of support."

Santos has pushed through several policy changes to tackle structural economic defects that prompt support for the FARC, such as returning land stolen by right-wing paramilitaries and rebels to displaced peasants.

The attack underscores the ability of the FARC to harm the nation's economic infrastructure and civilian population even after a decade-long offensive severely weakened the group and killed a number of its leaders.

Flight-security setback

The radar, which spans about 300km, provides coverage not only for civil aviation but for the fight against drug trafficking in the country.

Repairs on the radar will take several months, Santiago Castro, director of the civil aviation authority, said.

"The solution to prevent problems to the security of flights is to space them out," Castro said. "We don't know if there will be reductions in flights, but there will be delays."

The FARC is considered a terrorist organisation by the US and Europe. The military offensive has dealt major blows to the FARC in the past several years and cut cocaine output in one of the world's top producers of the drug.

Security improvements have drawn record foreign investment to the Colombian economy, mostly into the oil and mining industries. Still, the security gains mask deep-seated issues like unequal land distribution, rural poverty, flourishing criminal gangs and weak institutions.

Both the FARC and the government have called for peace, but Santos says the fighters must first prove they want peace and release all hostages and stop attacks.

FARC has so far refused to disarm.