At least eight suspected gang members have died in a gun battle with Mexican marines in Mexico City.
The capital had largely been spared the worst of the country's drug violence as well as the street blockades set up by drug cartel supporters, until now.
The Mexican Navy said in statement that a patrol of marines in Tlahuac, in the southeastern part of the city, was attacked by suspected gang members, sparking the gunfight.
The dead included Felipe de Jesús Pérez Luna, also known as "The Eyes".
The 48 year old is said to have been the head of the group called Cartel de Tláhuac.
He has been linked to about 50 killings, including the death of the Mexican State Attorney General, Felipe Carmona, in February 2016.
Perez Luna's son Miguel Angel, was arrested on May 22 by the Attorney General's Office in Acapulco.
The Navy said the gunmen were suspected of drug dealing, extortion, murder and kidnapping.
It did not say if any of the marines were injured.
They had been sent to the area to follow up on intelligence about the whereabouts of local criminal gangs.
To prevent the arrival of police and military reinforcements, dozens of people blocked streets in the district of La Conchita Zapotitlán, a populous neighborhood in the southwest of the city.
A truck and two minibuses were stolen and set on fire.
The tactic has become known as "narco-blockades" in Mexico and had been confined to the north and west of the country.
Drug cartels have been using the strategy for several years to try to stop raids by the security forces as well as to intimidate local residents.
Youths also clashed with the security forces during the incident in Mexico City.
At least 15 people were arrested.
The exchange was one of the most violent clashes between security forces and gangs since 17 suspected gangsters were killed in northwestern Mexico at the end of June.
Since 2007 when former President Felipe Calderon launched his assault on drug cartels, Mexico City has largely avoided the violence that has plagued much of the country and resulted in more than 100,000 deaths.
But attacks have been rising in the Mexican capital according to Interior Ministry data.
In the first five months of 2017, there were 438 murders, up almost 20 percent on the same period last year.