A Colombian soldier inspects a coca plant at a 20 hectare plantation found by the army/File photo

BOGOTA: At least six farmers protesting the removal of coca crops, the base ingredient in cocaine, were killed during a confrontation in rural southwestern Colombia, President Juan Manuel Santos said on Friday.

Santos ordered further investigation into the event, which took place on Thursday and also injured 19 people. The incident occurred in Narino province, near Tumaco, a key zone for coca growing.

Reports on how exactly the six people died were contradictory.

The defense ministry said on Thursday that a dissident group of ex-fighters from the Revolutionary Armed Forces of Colombia (FARC) rebel group forced farmers to protest against police who were removing coca crops. The dissidents then fired on the officers and launched home-made missiles, hitting the farmers, the ministry said.

But regional farmers? organizations accused the police and army of firing at the civilians to break up the protest and clear the way for the manual eradication of the crops.

The majority of FARC fighters demobilized under a peace deal signed last year, but some dissident units remain involved in drug trafficking and illegal mining. The FARC, now a political party, has distanced itself from the dissidents.

?We are verifying the exact way in which things occurred,? Santos said during a press conference. ?We are investigating, I don?t want to tie myself to any version of events until these investigations give us total clarity about what happened.?

The events underlined the significant challenge that the drug trade represents to the peace process with the FARC, the head of the United Nations? mission in Colombia said.

?The events reinforce our conviction at the United Nations of the necessity of giving coca farmers in affected regions all the means to escape the terrible choice between extreme poverty and illegality,? mission chief Jean Arnault told journalists.

Subsistence farmers have often been obliged by rebel groups, paramilitaries and crime gangs to plant and harvest coca. Some also choose to grow the crop because illegal groups will pay more for it than farmers can earn at market with other products - a tempting possibility amid dire poverty.

Coca cultivation reached levels not seen for a decade last year after the government banned aerial fumigation with glyphosate, an herbicide that has been linked to cancer. The prohibition has sparked criticism from the United States, which is set to give the Andean country more than $400 million in funding help for the FARC deal.

Coca is cultivated on about 188,000 hectares (464,000 acres) across Colombia. The government wants to manually eradicate 100,000 hectares this year.