Mexico has struck a major blow against a faction of the violent Zetas cartel with the capture one of the country's most-wanted drug traffickers, Iván Velázquez Caballero.
Velázquez, known as El Talibán, has been fighting a bloody internal battle with Zetas' leader, Miguel Angel Trevino Morales, and officials have said the split was behind a recent surge in massacres and shootouts, particularly in the country's north.
"A person who is presumed to be, and acknowledges being, Iván Velázquez Caballero was captured in the state of San Luis Potosi" in north-central Mexico, the navy said on Wednesday.
Velázquez, also known as Z-50, has a 30m peso (£1.4m) reward on his head.
If confirmed, the arrest could calm some of the violence that has spread through border cities such as Nuevo Laredo in recent weeks.
On 14 September eight men were found shot dead while another was discovered hanging from a bridge in Nuevo Laredo, territory traditionally controlled by Trevino, also known as Z-40. Analysts say 14 bullet-ridden bodies stuffed in a van in mid-August in San Luis Potosi were men loyal to El Talibán and may have been left there as a warning by Trevino's underlings.
Discussing recent fighting, a US official in Mexico, who could not be named for security reasons, said this week: "I think right now the uptick that I'm seeing is between 40 and 50," referring to Trevino and Velázquez.
The Zetas cartel takes its name from a police radio code in which Z means commander and a number refers to rank.
The official said Velázquez appeared to have formed an alliance of convenience with the Knights Templar cartel based in southern Michoacán state for his fight with Trevino.
Banners signed by Zetas members and hung from flyovers in several Mexican states appeared to confirm mutual hatred between Trevino and Velázquez. In the obscenity-filled banners, the men accused each other of betraying their fellow traffickers and preying on civilians.
If the detained man is confirmed as El Talibán, the development could strengthen Trevino, who shares leadership of the Zetas with Heriberto Lazcano, whose alias is El Lazca.
The US official played down speculation that Trevino and Heriberto were feuding. "I'm not familiar with a fight between him (Trevino) and Lazca," the official said. "I think they're still together, from what I understand."
Legislators and rival drug lords portray Trevino as an assassin who eliminates rivals by stuffing them into oil drums, dousing them with petrol and setting them alight, a practice known as a guiso (stew).
The Zetas are considered the region's most violent criminal organisation. They have been blamed for a large proportion of the tens of thousands of deaths in Mexico's war on drugs, though other gangs also have committed mass killings.
Gun battles between navy personnel and gunmen broke out late on Wednesday in the city of Piedras Negras, across the border from Eagle Pass, Texas.
Officials in the border state of Coahuila confirmed the shootouts. The state security spokesman, Sergio Cisbeles, said the confrontation was serious but could not confirm whether anyone was wounded or dead.
The Zetas have previously been active in Coahuila but it remains unclear whether the confrontations in Piedras Negras are linked to the capture of Velázquez.
