Four people died in shootouts with army troops in Reynosa, a border city in the northeastern Mexican state of Tamaulipas, state officials said.
The first shootout occurred around 1:50 p.m. in the Mil Cumbres section of Reynosa, located across the border from McAllen, Texas, the Tamaulipas Public Safety Secretariat and the Attorney General's Office said.
State police and crime scene investigators confirmed that a man from the southern state of Chiapas died in the shootout, officials said.
"Rifles and a 2007 model Jeep Liberty vehicle with tags from the state of Texas (United States) were seized," state officials said in a statement.
The second shootout happened a few hours later in a field in the Lomas del Real de Jarachina Sur district, where three people died in a firefight with army troops.
Soldiers seized several large-caliber firearms and a GMC pick-up truck with Texas tags following the shootout.
"In response to these incidents, criminal organizations staged street closings in several parts of the city with heavy vehicles and public trucks in an effort to prevent the armed forces and police from deploying," state officials said.
Gunmen forced people out of their automobiles and used the vehicles to block some of the main avenues in the border city.
The security forces responded immediately and moved the vehicles, allowing traffic to flow once again, officials said.
A shootout involving the army in Ciudad Victoria, the capital of Tamaulipas, left seven people, including Los Zetas drug cartel boss Carlos Barriento, dead on Monday.
The army is carrying out "Operation Northeast" in the states of Nuevo Leon, Tamaulipas, Coahuila and San Luis Potosi in an effort to weaken the drug cartels that operate in the region.
The Gulf drug cartel has been waging a war in northeastern Mexico against Los Zetas, a band of army special forces deserters turned hired guns and drug traffickers.
After several years as the armed wing of the Gulf cartel, Los Zetas went into the drug business on their own account and now control several lucrative territories.
More than 50,000 people, according to official figures, have died in drug-related violence in Mexico since late 2006, when President Felipe Calderon took office and declared war on the country's powerful drug cartels.
Calderon has deployed tens of thousands of soldiers and Federal Police officers across the country to combat drug cartels and other criminal organizations.
The use of the armed forces to fight drug traffickers, however, has failed to stem the violence.
Mexico registered 27,199 murders in 2011, or 24 per 100,000 people, the highest number since Calderon took office, the National Institute of Statistics and Geography, or INEGI, said in a report released on Aug. 20.
The Movement for Peace with Justice and Dignity, which was founded by human rights activist and poet Javier Sicilia, puts the death toll from Mexico's drug war at 70,000. EFE