MEXICO CITY - Mexican marines killed a reputed Gulf cartel leader and one of Mexico's most-wanted drug lords in a spectacular, hours-long gunbattle near the U.S. border, the latest in a growing number of hits on the country's drug kingpins.

Antonio Ezequiel Cardenas Guillen, also known as "Tony Tormenta" or "Tony the Storm," was killed Friday along with four of his gunmen and three marines in the city of Matamoros, across from Brownsville, Texas, the Mexican navy said in a statement.

President Barack Obama telephoned his Mexican counterpart, Felipe Calderon, Saturday morning to reaffirm Washington's support for Mexico's efforts to fight the cartels and express his condolences for the Mexican troops and the reporter killed in the shootouts, according to a White House statement.

A soldier and a local reporter were also killed in related mayhem that began Friday morning and lasted into the evening. Across the city, residents holed up in their homes and offices to escape the violence, communicating by Facebook and Twitter.

"Shelter, everyone! Don't leave your houses please. Pass the word," read one tweet.

Dozens of banners apparently signed by the Zetas, a Gulf cartel rival, appeared Saturday in northeastern Tamaulipas state and neighboring Veracruz state.

Each of the signs - hung on pedestrian overpasses and in other public places but quickly taken down by authorities - bore the same poorly written and obscure message: "Once again the destiny of the traitors has been demonstrated, crushing the Gulf traitors."

Veracruz Public Safety Secretary Sergio Lopez said authorities were investigating but did not know if the banners were a reaction to the death of Cardenas Guillen.

Drug gangs used vehicles to block several roads in the nearby city of Reynosa, across the border from McAllen, Texas, according to Twitter messages sent out by the city government warning residents to be careful.

It was unclear if the roadblocks were related to the shootings Friday. City governments in Tamaulipas - reacting to violence that is often between federal forces and drug gangs - routinely warn citizens of roadblocks and shootouts through Twitter messages.

Cardenas Guillen, 48, is believed to have run the powerful cartel along with Jorge Eduardo Costilla Sanchez, moving cocaine and marijuana into the United States. He had been indicted on drug-trafficking charges in the U.S., where authorities had offered a $5 million reward for information leading to his arrest. Mexican authorities offered a $2 million reward and had him on their list of the nation's most-wanted drug traffickers.

He was killed in a two-hour shootout in an operation that included 150 marines, three helicopters and 17 military vehicles and that was the result of more than six months of intelligence work, the Mexican navy said in a statement. The navy said troops showing up to arrest Cardenas Guillen were met with grenades and heavy weapon fire. Gun battles had raged throughout the city since the morning.

The Matamoros newspaper El Expreso said on its website that reporter Carlos Guajardo was killed covering one of the shootouts. Local news media reported Guajardo was leaving the area of the clash when his car was hit by gunfire more than 20 times.

Reporters at nearby El Expreso huddled in the newsroom and for hours published nothing on its website about the violence except for their colleague's death. A brief story Saturday morning detailed the shootouts, saying they "caused chaos and panic among the population." The story said nothing about the death of Cardenas Guillen.

A video posted on YouTube showed a string of SUVs and pickup trucks with gunmen racing through an empty street while continuous shooting was heard in the background. Men wearing ski masks got out of a car and used it to block the street.

The gunfire started as early as 11 a.m. at an upscale residential area in Matamoros, according to a resident who didn't want to be named for fear of retaliation.

The deceased trafficker's brother Osiel Cardenas Guillen led the Gulf cartel until his arrest by Mexican authorities in a similarly violent shootout in Matamoros in 2003. Osiel was extradited to the United States in 2007 and sentenced to 25 years in prison by a Texas court in February.

The banners that appeared Saturday morning mentioned the "informer Osiel," but it was impossible to be sure what was meant by the reference.

Northeastern Mexico, an area once controlled by the Gulf cartel, has seen an increase in violence due to a turf battle between the cartel and the Zetas, a drug gang formed by ex-military special forces originally as the assassins for the cartel. The violence has included broad-daylight shootouts and dozens of beheaded corpses dumped in public areas.

Cardenas Guillen's death is a major boost to Calderon's war on drug cartels.

"Today, we have taken another meaningful step toward the dismantling of criminal groups that do so much damage to our country," said Alejandro Poire, presidential security spokesman.

Arturo Beltran Leyva, leader of the Beltran Leyva cartel, died in a raid outside Mexico City on Dec. 16, 2009. Mexican soldiers killed the Sinaloa cartel's No. 3 capo, Ignacio "Nacho" Coronel, on July 29 of this year. On Aug. 30, federal police announced the capture of Edgar Valdez Villarreal, alias "La Barbie," and on Sept. 12 Mexican marines captured Sergio Villarreal Barragan, another presumed Beltran Leyva leader.

More than 28,000 Mexicans have been killed in drug-related violence since Calderon launched a national assault on organized crime in late 2006. The Committee to Protect Journalists said in a recent report that at least 22 Mexican journalists have been killed since December 2006.