In a city known for violence, authorities have launched a campaign to get guns off the street.

Police chose a slum in Ciudad Bolivar perched on a barren mountain in the outskirts of Bogota as the first place to enforce a new ordinance restricting the carrying of weapons.

Police officers stopped cars, vans and buses to check its occupants, most of whom agree with the law.

"At least I know there is no thief on the bus and that they are not going to attack me," Jose Mauricio Moreno, a 35-year-old salesman, told AFP.

Bogota, with a population of more than 7 million people, recorded 1,632 homicides last year. City administration figures show 62.3% of them were committed with firearms.

Bogota's new mayor, Gustavo Petro, a 51-year-old former leftist guerrilla, announced just after taking office that carrying weapons is now restricted in public places and on the streets.

The ordinance does not apply to public security forces, private guards found throughout the capital, and guards of diplomats or ministers.

But city officials aim to "discourage the use of arms" and raise awareness among citizens about the "futility and danger of carrying a firearm," Petro said when he launched a campaign called, "To arm or to love. Yes to citizen disarmament."

However, the ordinance has provoked strong criticism from Petro's opponents, who say the mayor is undermining civil liberties.

Some security experts doubt the ban will lower the crime rate, saying nearly all homicides in Bogota are committed with illegal weapons.

Alfredo Rangel, an analyst at the Security and Democracy Foundation, said the measure has popular and media appeal but will have only a "marginal effect" on crime.

"It has nothing to do with crime," Rangel told AFP. "People who own legal firearms are not the ones who go rob banks."

In Medellin, Colombia's second largest city with 2.3 million residents, a gun ban has been in effect for three years but the homicide rate rose 7% in 2011, Rangel said.

The homicide rate in Bogota in 2011 was 21.5 per 100,000, well below major Colombian cities of Cali (77.9 per 100,000) and Medellin (70.3 per 100,000). Both cities are former drug cartel strongholds where criminal gangs still proliferate.

Colonel Alvaro Bermudez, Ciudad Bolivar's police commander, agreed the gun ban "will not change the world" but it might stop "someone who is going to have a beer, who would pull a gun after a few drinks in a small scuffle."

Violations of the law allow police to permanently confiscate guns, among other penalties.

Supporters of the ordinance include Alirio Lopez, a priest who for 14 years has promoted youth disarmament in his parish.

The gun ban "is on the right track. What matters is a change of mentality, that people realize that a gun does not make you stronger," said the priest, who is known popularly as "Father Tolerance."