Valdemar Quintanilla Soriano was captured in the northern city of Saltillo in Coahuila state, where weapons and cash were also found.

Another Zetas suspect, Jose Guadalupe Yanez Martinez, was also detained.

The Zetas and the Gulf Cartel are in a bloody battle for control of drug smuggling routes to the United States.

"During the last months, Quintanilla Soriano often travelled to Monterrey in Nuevo Leon, Saltillo and Monclova in Coahuila to coordinate finance matters as well as the payment to authorities working for the criminal organisation," said Colonel Ricardo Trevilla, spokesman for Mexico's National Defence Secretariat.

Another key Zetas suspect, Jesus Enrique Rejon Aguilar, was arrested a month ago.

The Zetas were formed by former Mexican special forces soldiers.

Mr Rejon was a member of the Mexican special forces but deserted in 1999, officials say.

The Zetas initially acted as armed enforcers for the Gulf Cartel.

The Zetas have since split with their former paymasters, and have been engaged in brutal turf wars for control of smuggling routes.