Two weeks ago his brother Arturo, reputed head of the Beltran Leyva cartel, was killed in the central city of Cuernavaca. He was the highest-ranking cartel suspect to be killed or captured since the president, Felipe Calderón, deployed tens of thousands of soldiers and police three years ago to fight drug gangs.

Officials have previously described Carlos Beltran Leyva, 40, as a key member of the gang, but it was unclear whether he took over as chief after his brother died.

A third brother, Alfredo, was arrested in January 2008. At least one other, Mario, remains at large and is listed as one of Mexico's 24 most wanted drug lords, with a $2m reward offered for his capture. Carlos was not included on the list, although the public safety department said there had been a warrant for his arrest since 2008.

Officials from the US Drug Enforcement Administration, which helped to track down Arturo, said one of the brothers was likely to have filled the void. The agency's intelligence chief, Anthony Placido, said last month the US was receiving reports of plots to break Alfredo out of prison.

Days after Arturo's death, gunmen killed the mother and three other relatives of a marine who died in the shootout. Calderón vowed he would not be intimidated, but authorities were far quieter in announcing Carlos's capture, waiting three days to make news of the arrest public.

In a terse statement, the public safety department said police found him on Wednesday carrying two guns, ammunition and a false driver's licence identifying him as Carlos Gamez Orpineda. He later acknowledged he was Arturo Beltran Leyva's brother, the department said.

While a victory for the Calderón government, the downfall of the Beltran Leyva brothers has raised fears of an intensified turf battle over areas controlled by the beleaguered cartel, leading to more deaths in a war that has already killed more than 15,000 people since Calderón took office in 2006.

The bound and beaten bodies of two men were found on Wednesday hanging from a highway overpass in the Sinaloa town of Los Mochis. Nearby, a message written on a piece of cardboard said in part that "this territory already has an owner".