The annual event celebrating "world weed day" was the first since Colorado began selling the drug for recreational use in licensed shops on Jan 1.

In America's first cannabis-legal state it is still not permitted to smoke the drug in public spaces outdoors.

But many the crowd ignored signs to that effect and a thick fog of cannabis fumes rose over Civic Center Park next to the Colorado state capitol. Armed security was present but largely ignored infringements.

Police said a total of 130 people were arrested or issued on-the-spot fines. Of those, 92 were for public consumption of cannabis and 22 people "went to jail".

Tourists had flooded into Colorado for the event and 20 of those either arrested or fined were from outside Colorado. The fines were $150.