Mexico has captured a key figure in the Zetas drug cartel who allegedly ordered the torching of a casino in August, one of the country's worst-ever attacks which burned 52 people alive. Carlos Oliva Castillo, alias "La Rana" (The Frog), 37, was considered the number three and right-hand man of the cartel's chief and allegedly ordered the attack on the Casino Royale in Monterrey, an army spokesman said Thursday. He was detained in Saltillo, northern Coahuila state, on Wednesday as gang members unleashed a hail of gunfire in an apparent failed attempt to cover his escape, according to a defense ministry statement. The suspect "is considered the operational chief for the criminal operations of the Zetas criminal group in Coahuila, Nuevo Leon and Tamaulipas states," it said. He was allegedly a top lieutenant of cartel chief Heriberto Lazcano. The arrest followed running street battles involving troops, police and gang members in which a taxi driver was killed and eight other people were wounded, including three police, the Coahuila state prosecutor's office said. The operation was part of an army operation named Scorpion started in early August and which has led to the arrest of 724 suspected criminals and the seizure of weapons and $1.5 million. The arrest came shortly after the United States accused Iranian operatives of having tried to contact a Mexican drug cartel as part of a plot to kill the Saudi ambassador in Washington. Officials did not specify which of Mexico's powerful cartels was allegedly approached, but US media reported that it was the Zetas, a notorious drug cartel made up of former Mexican special forces. The Zetas, who started out as hitmen working for the Gulf cartel in the 1990s, have been accused of a string of killings, kidnappings and macabre displays of brutality that have made them one of the most feared gangs in Mexico, as well as Guatemala. Some 45,000 people have been killed in drug-related violence since Mexico launched a massive military operation against the cartels in 2006, according to officials and news reports.