MEXICO CITY (AP) -- Mexican marines captured 30 suspected Gulf cartel members and seized an arsenal of weapons during two days of raids in a northern border state torn by drug gang battles, officials announced Wednesday.

The marines, acting on intelligence obtained by the navy and other agencies, conducted the raids in Matamoros and Reynosa, two cities across the border from Texas in the state of Tamaulipas, Rear Adm. Jose Luis Vergara said.

The troops seized more than 50 guns, two shoulder-fired rocket launchers, 21 grenades and ammunition.

The 30 suspects, including one woman, were paraded before reporters at an air base in Mexico City, handcuffed and flanked by masked marines in black-and-white combat gear. They were lined up in front of a helicopter, the arsenal of weapons laid out in front of them.

Despite the display, the navy gave no indication of how significant the arrests were in the government's efforts to destroy the Gulf cartel, which is waging a bloody turf war in Tamaulipas with its former ally, the Zetas gang of hit men.

Vergara said all 30 are believed to belong to the Gulf cartel but gave no details on their alleged roles in the gang. He took no questions.

Parading drug suspects in front of the media is a near-weekly ritual in Mexico that has come under increasing criticism from human rights groups.

Last week, opposition politicians grilled Public Safety Secretary Genaro Garcia Luna about the practice during a congressional hearing, calling it propaganda meant to deflect the public's concerns over the power of drug gangs.

According to a report President Felipe Calderon gave to Congress this month, just 12 percent of criminal investigations under his administration have ended in convictions. Government figures obtained by The Associated Press earlier this year show that three-quarters of the drug suspects arrested since Calderon took office in late 2006 have been freed.

Drug-gang violence has claimed 28,000 lives since December 2006, when Calderon deployed thousands of troops and federal police seeking to wrest territory from the drug lords.

Since the split between the Gulf and Zetas gangs this year, Tamaulipas and neighboring Nuevo Leon state have seen some of the most horrific attacks, including the assassination of a gubernatorial candidate and several mayors and the August massacre of 72 migrants.

In the latest violence in the border region, attackers threw an explosive at city hall in Matamoros early Wednesday, injuring three people, the federal Attorney General's Office said.

Also on the border, two federal police officers were slain Wednesday at a downtown hotel in Ciudad Juarez, a city across from El Paso, Texas, that has become one of the world's most violent places amid fighting among rival drug gangs.

A police official, who insisted on anonymity, said the two officers were part of the federal police's intelligence operation.