Authorities in Mexico say they have arrested an alleged leader of a major drug cartel, Los Zetas, as thousands of federal police have been deployed across the country in an effort to stem a staggering number of homicides.

Jose Maria Guizar Valencia, a dual US-Mexican citizen known by his Zetas code name "Z 43", was arrested on Thursday in Mexico City, Mexican federal officials said on Friday.

The US had offered a $5m reward for information that could lead to Valencia's arrest and has already requested his extradition.

Al Jazeera's Manuel Rapalo, reporting from Cancun, said Valencia had been evading the authorities since 2014.

He faces several drug trafficking charges in the US states of Texas and Virginia, the US Bureau of International Narcotics and Law Enforcement Affairs says on its website.

Valencia had "complete command and control of his own faction" of Los Zetas in southern Mexico, the bureau said, and is accused of being "responsible for the importation of thousands of kilogrammes of cocaine and methamphetamine" into the US every year.

Record number of homicides

The high-profile arrest comes as 5,000 Mexican federal police officers are being deployed to cities across Mexico to fight a recent surge in homicides.

About 25,000 people were murdered in Mexico last year, the highest tally since the country began keeping records two decades ago.

"Most homicides are related to organised crime. They are committed by criminal groups competing for control over other criminal groups. All of it is related to the sale of drugs," Darwin Puc Acosta, chief of police in Cancun, told Al Jazeera.

About 4,000 police officers have already been sent to Tijuana, Cancun and the state of Baja California Sur, among other places, since the start of the year.

The deployment "is part of a larger strategy that's been going on to curb back the violence in the country for well over a decade now," Al Jazeera's Rapalo explained.

But security analysts have criticised Mexico's strategy and the increased militarisation of the country's police force.

Civil society activists, meanwhile, say the deployment of security forces has not served everyone equally: while police patrols may have increased in predominantly touristic areas, they say residential and other neighbourhoods continue to see widespread violence.

"The decisions of the federal government are to protect the hotel industry," said Rosa Maria Marquez, an activist in Cancun.

"But what about the ones that work in that industry and then return to the areas where crime and violence prevails?"

Rapalo said the focus in Cancun has indeed been on protecting the city's reputation as a major destination for holidaymakers. Cancun's tourism industry brings in a third of all such revenues generated in the country.

But he said the increased police presence ultimately aims "to prevent that violence from 2017 from spilling over into new territories and new cities in Mexico".