Police detain a man who was blocking traffic during a protest against a decree by Colombia's President Ivan Duque that would allow police to confiscate any amount of drugs from people in the street in Bogota, Colombia, Thursday, Sept. 6, 2018. In 2012, Colombia's Constitutional Court approved a government bill to decriminalize the possession of small quantities of drugs for personal use. (AP Photo/Fernando Vergara)

Police detain a man who was blocking traffic during a protest against a decree by Colombia's President Ivan Duque that would allow police to confiscate any amount of drugs from people in the street in Bogota, Colombia, Thursday, Sept. 6, 2018. In 2012, Colombia's Constitutional Court approved a government bill to decriminalize the possession of small quantities of drugs for personal use. (AP Photo/Fernando Vergara)

BOGOTA, Colombia (AP) — Riot police have broken up a pro-marijuana demonstration in Colombia’s capital city, as the South American country takes a harder stance on drugs.

Dozens of people showed up at Bogota’s planetarium Thursday with posters and small amounts of marijuana to stage a “smoke-a-thon” to defend recreational use of the plant.

But the crowd was dispersed by police in riot gear minutes after protesters began to light up their marijuana cigarettes. At least half a dozen people were arrested as clashes broke out.

Colombia’s constitution enables marijuana users to possess small doses meant for personal consumption. But new President Ivan Duque is tightening drug laws and recently issued a decree that enables police to confiscate any drug consumed in public.