MEXICO CITY (AP) — Burnt-out vehicles. Road blockades. A raging gun battle between armored marines and gang members that left eight dead.

Such scenes have been common in border cities like Reynosa and Nuevo Laredo, and figures released Friday show the death toll from Mexico's drug war has reached new heights this year. But residents of the capital were stunned this week to see that kind of mayhem in their own city.

Thursday's shootout, along with the recent emergence in a working class neighborhood of an apparent group of "vigilantes" — styled after self-defense militias that rose up against a drug cartel in the western state of Michoacan — have left authorities scrambling to maintain their long-held claims that drug cartels don't operate in Mexico City.

Thursday's shootout saw some 1,300 police and marines deployed on the streets of Tlahuac, a poor borough on the southeastern outskirts that was a rural area until a few years ago. Photos from the scene showed the slain suspects were carrying assault rifles instead of the pistols usually used in most armed crimes in Mexico City.

Perhaps most shocking was the appearance of organized roadblocks put up by gang members or sympathizers to impede the movements of police. City officials said gang members hijacked about five buses or trucks, and video images showed teams of motorcyclists parking their vehicles to shut down an expressway and then setting fire to a bus after the passengers fled.

"The narco-blockades come to Mexico City," the newspaper El Universal wrote in a front-page headline Friday.

The nation's capital once looked on the drug war as a battle fought in outlying states. Not anymore. The capital's violence is still far from the worst, though its murder rate went up by 21 percent in the first six months of this year, according to the newly released government security statistics.

Those show homicides over the first half of the year increased 31 percent over the same period last year, in the worst bout of such violence in at least 20 years — even worse than the previous peak year of 2011.

But unlike 2011, when the violence was largely concentrated in border states like Chihuahua and Tamaulipas — where Reynosa and Nuevo Laredo are located —homicides are now on the rise throughout the entire country, making much of the country look like a hotspot.

In Thursday's clash, swarms of motorcycle rickshaws, a form of taxi with a canopied metal seating unit towed behind the vehicle, were used for the blockades. Police hauled off 47 of them and arrested 16 suspects, many of them carrying their helmets.

Operators of the unregulated rickshaws "apparently maintained links with drug dealing, involving distribution," Mexico City police said in a statement.

Officials estimate there are about 5,000 of the unofficial cabs in the borough and have tried to eliminate then in the past. But in outlying areas where roads are rough, the rickshaws remain the transportation of choice for many residents who can't afford to own a car or pay a regular taxi fare.

Raul Benitez, a security expert at the National Autonomous University of Mexico, said the gang, led by man nicknamed "The Eyes," employed a network of those drivers to distribute drugs and act as lookouts.

"They were using high-powered rifles, not pistols, which justified the government's decision to use the marines," Benitez said.

The marines, considered Mexico's most elite troops, have been deployed in other urban settings before, using helicopter-mounted machine guns against drug suspects. But outside of occasional patrols or other operations, they are seldom seen in the capital such numbers.

Mayor Miguel Angel Mancera denied that the eight men killed in the shootout were members of a cartel, instead claiming that "a big gang of street-level drug dealers" was involved.

However he acknowledged "they had control" of the area and used some cartel-style tactics such as moving in armed convoys and putting up signs similar to those seen in cartel strongholds.

"We will neither tolerate vigilantes nor criminal groups in Mexico City," Mancera said at a news conference Friday.

Traditionally authorities have said the city's traffic is too congested, and there are too many police officers — over 80,000 — for drug traffickers to move in convoys as they do other states.

The official line has been that while the gangs may have laundered money and sold drugs in the capital, they avoided the kind of unchecked violence seen elsewhere so as to not disrupt urban life and attract attention to themselves.

But the gang run by "The Eyes" evidently took on some trappings of the cartels, such as territorial control of drug dealing, wide-spread extortion of businesses, the use of assault rifles and the elimination of rival traffickers.

"This type of gang ... generally doesn't operate in Mexico City's main districts. They operate in poorer outlying areas," Benitez noted, saying that by contrast, gangs in the city center are more sophisticated and keep a lid on the violence.

Thursday's shootout "doesn't cause panic in the whole city because it occurred in an outlying area," Benitez said. "But it should be a wake-up call, because if it isn't stopped quickly, drug cartels could enter the city."

In Puebla, a state near the capital which had also previously been relatively quiet, authorities said Friday that a Navy operation to capture the leader of the state's principal fuel theft ring resulted in the death of four suspects and one marine.

Two other marines were wounded and authorities were working to identify the dead.