By GINGER THOMPSON and JAMES C. McKINLEY Jr.
 
MEXICO CITY, Jan. 13 - Prisons have not contained the drug war.

In the last four years, Mexico has made unprecedented advances in its fight against drug cartels by capturing many of the country's most powerful kingpins. Now, however, a new wave of drug-related killings has made clear that cartel leaders have begun to regroup, and are waging deadly campaigns from Mexico's maximum security prison to keep control of their territories.

At least 34 people, including 3 federal agents and 2 journalists, have been assassinated since June in the struggle. The authorities are reporting alarming spikes in drug-related violence from Cancún in the south to cities along Mexico's northern border with the United States.

"The fact of having incarcerated them does not in any way guarantee that they will not commit acts of violence," said Mexico's assistant attorney general for organized crime, José Luis Santiago Vasconcelos. "They are always looking for ways to undermine and destroy legal systems, to destroy prison systems and surveillance systems to keep operating."

Law enforcement officials said that at the epicenter of the recent violence is a mercurial drug dealer named Joaquín (El Chapo) Guzmán Loera, who broke out of prison in January 2001 hidden inside a laundry truck, and now seems determined to seize this country's principal drug routes. While other cartels have been weakened by the arrests of their top leaders, Mr. Guzmán has rebuilt his organization, turned former foes into allies and moved to expand his territory.

The authorities said Mr. Guzmán had waged a war on two fronts, attacking the Gulf Cartel, which controls the eastern border crossings with Texas in the state of Tamaulipas, and the Arellano Félix organization, which controls the western border between Tijuana and El Paso.

Desperate to stop him, the leaders of those beleaguered cartels - once archenemies - have also formed an alliance, hired a team of former special forces officers as hit men and orchestrated vicious counterattacks from Mexico's principal maximum security prison, La Palma.

The authorities say Osiel Cárdenas Guillén, the leader of the Gulf Cartel who has been in prison since 2003, leads the fight against Mr. Guzmán. And they say he is joined by Benjamin Arellano Félix, the feared leader of the Tijuana cartel, who was arrested in 2002.

"What we have here is a merger, essentially," said John S. Fernandes, the special agent in charge of the Drug Enforcement Administration's San Diego office. "They are trying to solidify their forces."

The two imprisoned mob bosses are battling incursions from Mr. Guzmán and, to a lesser degree, from other leaders in the Ciudad Juárez cartel, among them Ismael (El Mayo) Zambada, Juan José (El Azul) Esparragoza and Vicente Carrillo Fuentes, law enforcement officials say. The realignment has produced a spate of revenge killings. In October, the authorities found five men believed to have been Mr. Guzmán's associates bound and shot execution-style in the border city of Nuevo Laredo. A note addressed to Mr. Guzmán was found with the bodies. It read, "Send more idiots like these."

A month later, nine bodies were found outside Cancún. Five of the bodies, including three federal agents, were found dumped in a field off the airport highway. The police reported that the victims had been bound, tortured and shot once in the head. Four other victims were found burned to death inside a car a few miles away. The murders stem from a struggle between Mr. Guzmán and Mr. Cárdenas over money-laundering operations in that tourist town, Mexican investigators said.

On New Year's Eve, Mr. Guzmán's brother, who was being held at La Palma, was shot several times at point-blank range in the prison visiting area. He was the second convicted drug dealer associated with Mr. Guzmán to be killed at La Palma within the last three months.

And just last weekend, four men were found murdered gangland-style in the southern town of Morelia while two others turned up dead in Tamaulipas state near the American border. Investigators say both incidents appeared to be drug-related shootings. In Tamaulipas, the killers left a note taunting "El Chapo" on the bullet-ridden bodies.

The authorities said at least two people had been killed each day so far this year in Mr. Guzmán's home state of Sinaloa, considered the Mexican capital of drug trafficking.

The violence has raised questions about President Vicente Fox's crackdown against drug traffickers, praised here and in the United States for capturing more than 100 drug traffickers, among them 15 most-wanted kingpins, and weakening the systems of protection that allowed them to operate with impunity.

Law enforcement officials here and in the United States say that the crackdown has so badly weakened the cartels that they have been forced into volatile alliances and rash attacks. They see the killings as the last spasm of organizations desperate to stay in business.

"They are breaking up," said Mr. Vasconcelos, the assistant attorney general. "They are trying to sustain their strength by whatever means. That is what we are seeing now."

Other experts on drug trafficking, however, say that the government's crackdown has done little to interrupt the flow of drugs through this country, nor to stem the corruption that allows drug traffickers to buy control of police and prisons.

In the wake of the increased law enforcement operations, these experts say, cartels have shifted alliances, and some have even begun operating in smaller units. But they have begun to bounce back, and so has the violence that comes with them.

"The good news is that the government of Mexico has arrested more kingpins and dismantled more cartels," said Jorge Chabat, an expert on organized crime at the Mexican research institute CIDE. "The bad news is that it means nothing. It hasn't stopped drugs from moving across the country. In fact, all it has done is created more violence."

Mr. Chabat added, "For many years, the United States complained that if Mexico did its job and put these kingpins in jail, then the drug war would end. But Mexico has done its job, and the war continues."

In a meeting with reporters on Thursday, Mr. Vasconcelos said the jailed drug bosses had used their lawyers to carry messages to operatives on the outside. He also said an untold number of guards had been bribed or threatened into cooperating.

At least five prison officials are being held in connection with the recent killings at the jail, including the director and two of his aides. And in the last week the government reinforced the security at La Palma, sending an additional 179 guards.

Jésus Blancornelas, a crusading Tijuana journalist who is one of the country's foremost experts on the drug trade, said adding officers to the prison would not change anything unless the rotten officers were removed.

"The problem in Mexico is that as long as you don't clean up the police, the drug trafficking system is going to continue working," Mr. Blancornelas said. "They say to me what do you have to do to capture the drug dealers, and I tell them, first, you have to capture the bad cops."