Image copyright Twitter @jaymrosenthal Image caption Police have blocked unlicensed dispensary chain in Toronto.

Toronto has used giant concrete blocks to bar entry to a chain of illegal cannabis dispensaries operating in the Canadian city.

The unlicensed chain has four locations and the city has been playing a cat and mouse game for months trying to shut them down.

The city calls them "blatant, repeat, and serial violators" of the rules.

Canada legalised recreational marijuana last year but only government-licensed stores are allowed to sell the product.

This week, Toronto bylaw enforcement officers, with the help of police, raided the four locations, seized the product on the premises and placed concrete blocks in front of them all to block entry.

The city has filed over 70 charges against employees, property owners and the businesses since last year, and police had issued several closure orders.

Whenever the stores were locked by police and bylaw officers, the owners would simply break back in and continue as before, said Mark Sraga, director of the city's investigation services.

"It got to the point where we've taken what we believe is a very significant and dramatic enforcement action," he said.

The blocks were removed within days at two storefronts by the dispensary operators, but were replaced by the city.

In an emailed comment, the "Cannabis and Fine Edibles" dispensaries called the move "a vigilante interpretation of flawed legislation".

Toronto resident Jay Rosenthal spotted the concrete barricades in front of one store on Tuesday.

Mr Rosenthal, who also heads a media company that focuses on the business of cannabis, said unlicensed stores have customers in part because of the time it has taken the province of Ontario to get its legal retail cannabis sector up and running.

Toronto currently has five licensed, legal cannabis stores.

"The province has been really slow approving new legal retail shops so the demand far outstrips the supply of legal shops," Mr Rosenthal told the BBC.

Image copyright Reuters Image caption Canada legalised recreational cannabis in October 2018.

Legal stores can also only sell a limited array of regulated products. Cannabis edibles, for example, will only come on the market in December.

Most unlicensed dispensaries in Toronto were shut down after cannabis was legalised last October. Over 90 illegal dispensaries were operating in the city before legalisation. Now there are fewer than 10.

Mr Sraga said the city plans to shut down the holdouts.

"We're not going to cease or stop our enforcement actions. Our goal is compliance," he said.