More than 5,000 Afro-Colombians blocked roads between the western province of Choco and the interior of Colombia to protest the aerial spraying of coca fields with pesticides.

The illegal harvests are sprayed from the air with glyphosate, a practice that has very bad effects on human health, food crops and water sources, an official with the Choco Intertribal Solidarity Forum, or FisChoco, told Efe.

The source, who requested anonymity, spoke with Efe by telephone from the regional capital of Quibdo and said that the fumigation began 11 days ago in coca-growing areas in 14 municipalities located in the Baudo and San Juan river basins.

The territories are the collective property of Afro-Colombian and indigenous communities, the source added.

None of the affected populations was consulted before the spraying was begun, despite the fact that legal regulations require it.

The spraying, which is aimed at eradicating some 4,000 hectares (9,800 acres) of coca, the raw material of cocaine, is the first of its kind in Choco, a region on the border with Panama and Colombia's richest reserve of biodiversity.

In protest, some 5,500 local residents on Sunday began a mobilization that on Monday blocked the passage of people and cargo between Choco and the country's interior along a highway that traverses Risaralda province.

The blockade has no end date, said the source with FisChoco, which gathers 58 community associations and has the backing of the Catholic Church.

FisChoco denounced the spraying, echoing a communique that the associated communities sent to President Juan Manuel Santos to warn him of the damage and ask him to order the immediate suspension of the operation.

According to the message, glyphosate - sold in the United States under the brand name Roundup - has caused injury to human health, affected legal crops and livestock and has contaminated water sources, including rainwater, which is channeled down into containers from the roofs of houses.

In the communication, the same communities warned that they do not accept the cultivation of coca in their territories, an activity that FisChoco attributes to rebels, paramilitaries and common criminals.