Image caption Police in Bogota checked motorists for guns on the first day of the ban

What might be one of the largest experiments in gun control ever attempted is currently under way in the Colombian capital, Bogota.

No weapons are allowed on the streets of this city of 7.3 million people from Wednesday until 30 April.

If the ban results in a significant reduction of the homicide rate it might become permanent.

The ban is being introduced by a former guerrilla - the city's Mayor Gustavo Petro.

"People who own guns legally can still keep them at their homes or at their offices. But they can no longer bring them to public places, carry them while on the streets, have them in their cars," Mr Petro's chief of staff, Antonio Navarro Wolf, explained.

"By doing so we will be protecting them from two things: from becoming a target for criminals who might want to take their weapons, and from using their guns in a moment of madness," said the former MP and governor of Narino, who demobilised from the left-wing M-19 group in 1990, just like Bogota's mayor.

Mr Navarro told the BBC he does not think Colombians are more prone to those "moment of madness" than other people.

But the fact remains that Colombia still is one of the most dangerous places on earth - the country with the fifth-highest rate of violent deaths in the world, after El Salvador, Iraq, Jamaica and Honduras, according to The Global Burden of Armed Violence 2011, a report issued by the non-governmental group Geneva Declaration.

'Bad guys won't care'

The country's high homicide rate is, of course, linked to ongoing armed conflict and to what Jorge Restrepo, a researcher with the Bogota-based Javeriana University, calls "formidable organised crime".

And critics of Mr Petro's ban have pointed out that most homicides involving firearms are committed with non-registered weapons, most likely smuggled into the country by left-wing guerrillas and the criminal bands that control drug trafficking.

Image caption Mayor Petro launched the three-month ban at a ceremony in Bogota

"The bad guys won't care about any ban, just as they don't care about any law," said Campo Elias Jarquin, a security guard.

But Mr Navarro remembers a study conducted in the 1990s that found out that one of every three murders involved legally acquired weapons.

"And the truth is, we really don't know" how many deaths by firearm involve legal weapons, he told the BBC.

"Very few of the guns used involved in homicides are ever seized by the authorities, only 10%. And with such small numbers is not possible to infer how many are legal and how many are not" Mr Navarro explained.

"What we do know is that there are legal weapons involved in homicides, especially in fights and acts of intolerance."

"And we know there were some 1,600 homicides in Bogota last year, and more or less 60% involved firearms," he said.

For Mr Restrepo, Mr Petro's idea has the potential to significantly reduce those figures, if properly enforced.

He contends that a gun ban actually has a bigger impact on armed criminals than on law-abiding citizens, because if apprehended criminals face not only losing their weapon but being arrested, and because criminals are more likely to carry guns than law-abiding citizens.

Past success

Mr Restrepo's empirical analysis of a ban put in place in several Colombian departments between November 2009 and January 2010 found a reduction of 23% in the number of gun homicides and of 53% in the number of gun injuries.

Because, for all the outcry provoked by Mr Petro's proposal, Colombia has experimented with gun bans before.

Partial bans - during the weekends or the festive season - have been in place both in the capital and other Colombian cities in the past.

And no weapons will be allowed on the streets of Medellin until January 2013, after the local authorities asked the army to impose a ban similar to the one requested by the mayor of Bogota.

The political significance of Bogota and its sheer size, however, have forced more people to pay attention.

And then there is also the symbolism of a ban coming from Mr Petro, in light of his past.

"From a political perspective it is very valuable that it is a former guerrilla, somebody who has already disarmed himself, who is asking citizens to also disarm," Mr Restrepo told the BBC.