Heavily armed fighters have surrounded security forces in a Mexican city and made them free one of drug lord Joaquin "El Chapo" Guzman's sons after his capture triggered gunbattles and a prison break that sent civilians scurrying for cover.
Security Minister Alfonso Durazo says a patrol by National Guard militarised police first came under attack from within a house in the city of Culiacan, 1200km northwest of Mexico City.
After entering the house on Thursday, they found four men, including Ovidio Guzman, who is accused of drug trafficking in the United States.
The patrol was quickly outmatched by cartel gunmen, however, and it was withdrawn to prevent lives being lost, the government said.
Simultaneously, fighters swarmed through the city, battling police and soldiers in broad daylight.
They torched vehicles and left at least one petrol station ablaze.
"The decision was taken to retreat from the house, without Guzman, to try to avoid more violence in the area and preserve the lives of our personnel and recover calm in the city," Durazo told Reuters.
The reaction to Guzman's capture was on a scale rarely seen during Mexico's long drug war, even after his more famous father's arrests.
The chaos continued as night fell. A large group of inmates escaped from the city prison. Residents cowered in shopping centres as gunfire roared. Black plumes of smoke rose across the skyline.
Cristobal Castaneda, head of security in Sinaloa, told the Televisa network that two people had been killed and 21 injured, according to preliminary information.
The chaos in Culiacan, long a stronghold for the Guzmans' Sinaloa cartel, will increase pressure on President Andres Manuel Lopez Obrador, who took office in December promising to pacify a country weary after more than a decade of drug-war fighting.
"El Chapo" Guzman led the Sinaloa cartel for decades, escaping from prison twice before being arrested and extradited to the United States, where he was found guilty in a US court in February of smuggling tons of drugs and sentenced to life in prison.
He is believed to have about 12 children including Ovidio. The US Department of Justice unveiled an indictment against Ovidio and another of the brothers in February, charging them with conspiracy to distribute cocaine, methamphetamine and marijuana in the United States.
Australian Associated Press