Marines killed four suspected gunmen who attacked them in the Mexican Gulf state of Veracruz over the weekend, state prosecutors said.

The shootout occurred Sunday in Cordoba, a city about 300 kilometers (186 miles) east of Mexico City, Veracruz Attorney General's Office spokesmen said.

Gunmen opened fire on a marine convoy around 7:00 a.m. in La Posta, a neighborhood in Cordoba, and the marines returned fire.

The shootout lasted nearly 30 minutes, with the combatants using assault rifles and fragmentation grenades, eyewitnesses said.

Investigators gathered evidence at the scene of the shootout, the AG's office said.

Officials did not say which criminal organization the dead gunmen belonged to.

On July 31, marines killed six suspected Los Zetas drug cartel members in two shootouts in Xalapa, the capital of Veracruz.

The shootout occurred near the limits between Xalapa and the city of San Andres Tlalnelhuayocan.

Veracruz has been plagued by a turf war between rival drug cartels that has sent the state's murder rate skyrocketing over the past two years.

The federal government launched "Operation Safe Veracruz" last October in an effort to stem the wave of drug-related violence in the Gulf state.

On June 12, police found the remains of 14 people stuffed into an abandoned SUV on the Alamo-Potrero del Llano state highway near Los Cuates, a ranch in northern Veracruz close to the border with Tamaulipas.

The Gulf, Los Zetas and Jalisco Nueva Generacion cartels, as well as breakaway members of the once-powerful La Familia Michoacana organization, are fueling the violence in the state.

Veracruz, Mexico's third-most populous state, is coveted as a key drug-trafficking corridor to the United States, officials say.

President Felipe Calderon declared war on Mexico's drug cartels shortly after taking office in December 2006, deploying tens of thousands of soldiers and Federal Police officers across the country to combat drug cartels and other criminal organizations.

More than 50,000 people, according to official figures, have died in drug-related violence in Mexico since late 2006.

The Movement for Peace with Justice and Dignity, which was founded by human rights activist and poet Javier Sicilia, puts the death toll at 70,000.

The violence has spiked this month, with the Mexico City daily Reforma reporting Saturday that 231 people were murdered across the country from Aug. 4 to Aug. 10, raising the death toll for the year to 6,309. EFE