Noel Salgueiro Nevarez is accused of running the Sinaloa cartel's operations in the northern state of Chihuahua, where drug violence is rampant.

Defence officials said his arrest would seriously weaken the cartel in Mexico and abroad.

The arrest was made on the same day as that of Martin Rosales Magana, who is accused of leading the La Familia gang.

The army said Mr Salgueiro Nevarez was seized in a carefully planned military operation, without a shot being fired.

Defence Ministry spokesman Ricardo Trevilla Trejo said Noel Salgueiro Nevarez was behind much of the extreme violence which has plagued Ciudad Juarez, Mexico's murder capital.

He said the suspect, also known as El Flaco (The Skinny One), led a gang of hitmen who extorted local businessmen, kidnapped for ransom, and tortured and killed members of a rival gang, the Juarez cartel.

'Criminal career'

The security forces say the bitter war between the two gangs was the trigger for most of the 3,000 killings in Ciudad Juarez last year.

Prosecutors said Mr Salgueiro Nevarez started his criminal career 15 years ago, producing marijuana for the Sinaloa cartel.

They said his gang had been exporting up to 15 tonnes of marijuana and two tonnes of cocaine per month to the United States.

The government had offered a three-million-peso ($220,000; £130,000) reward for information leading to his capture.

Security officials said his arrest, in the city of Culiacan in northwestern Sinaloa state, was a major blow to the Sinaloa cartel and its leader, Joaquin "Shorty" Guzman.

Mr Guzman, 54, is Mexico's most wanted man and thought to be one of the country's richest.

Two years ago, he made Forbes magazine's list of the 67 World's Most Powerful People. At number 41, he was just below Iran's Supreme Leader Ayatollah Ali Khamenei.

Crumbling cartel

Mr Salgueiro Nevarez's arrest was announced at the same time as that of another top figure in the Mexican drugs trade.

Martin Rosales Magana, 47, was seized in Mexico state on Tuesday. Police say he is one of the founders of the once-powerful La Familia cartel.

Until the beginning of this year, La Familia ran much of the methamphetamine trade in Mexico.

It claimed to protect local communities and promote family values, but also engaged in gruesome violence.

The security forces say it has been almost entirely dismantled, with its top leaders either in jail or dead.

They say Mr Rosales Magana lead a number of small cells still loyal to the cartel, which had holed themselves up in a rural area between Michoacan and Mexico state.

At a news conference, federal police counter-narcotics chief Ramon Pequeno described how La Familia splintered after the security forces killed the cartel's then-leader Nazario Moreno in December 2010.

He said part of the gang set up a rival cartel, which they named Knights Templar, and which quickly took over many of the methamphetamine labs in the west and south-west of the country.

Mr Pequeno said Mr Rosales Magana and those loyal to him tried to regain control of the drugs trade in Michoacan state by forging an alliance with their long-time rivals, the Zetas cartel.

He told reporters how "they met with the Zetas to ask for operational assistance, weapons and salaries [for gunmen] and expenses money, in order to recoup important cities held by the Knights Templar".

However, according to police, the alliance soon faltered because Mr Rosales Magane no longer had access to the precursor chemicals needed to make methamphetamine, their main source of income.

Mr Pequeno said with La Familia severely weakened, police would now focus their attention on taking down the Knights Templar.

Analysis

The Sinaloa Cartel controls the production of large quantities of heroin, marijuana, and methamphetamine (in the US) and boasts an extensive network of associates to facilitate its US trafficking operations, US officials say.

On Saturday, Texas Governor Rick Perry said he would even consider sending US troops into Mexico to combat drug-related violence and "keep the cartels off the border".

This is why the arrest of "The Skinny One" could be a severe blow to the Sinaloa cartel activity both sides of the fence.

It is also a public relations boost for Mexican President Felipe Calderon at home and in the US, amid growing criticism of his government's strategy to fight criminals and the drug trafficking.

Yet, the Sinaloa Cartel leader is still free. Joaquin "The Shorty" Guzman escaped from a maximum security prison in 2001, embarrassing the Mexican government.

Since then, he's become the number one target with a $3m reward for his capture.