MEXICO CITY – The U.S. Consulate General in the northern Mexican city of Matamoros counseled Americans to be careful while traveling in the eastern state of Veracruz in the wake of gangland violence that left 16 dead.

The emergency message posted on the consulate’s Web site also urged U.S. citizens in the part of Veracruz that borders San Luis Potosi and Tamaulipas states “to avoid intercity road travel at night.”

“Americans in this area should monitor local news and information to stay informed about situations that could affect their security,” the consulate said.

Before dawn on Thursday, a group of five gunmen attacked three buses on the Tempoal-Panuco highway in northern Veracruz, near the border with Tamaulipas, killing seven people.

Earlier, the same group had killed four other people in the town of El Higo, the Veracruz state Attorney General’s Office said in a statement.

After the attacks on the buses, army soldiers, marines and state police launched an operation to track down the criminals, leading to a clash hours later in which the five gunmen were reportedly killed and authorities also seized an armored vehicle, five rifles, 54 ammunition clips and eight cellular phones.

Veracruz is prized by organized crime as a key drug-smuggling corridor to the United States and as a route used each year by thousands of mostly Central American migrants, who are preyed upon by gangs and corrupt officials on their northward journey.

The Mexican government launched in October an operation dubbed “Safe Veracruz,” deploying federal forces and strengthening intelligence efforts to tackle a wave of drug-related violence in the state.

The effort was initiated after dozens were found dead in the Veracruz-Boca del Rio metropolitan area, including 35 bodies dumped on Sept. 20 on a busy thoroughfare in the Veracruz-Boca del Rio metropolitan area and 32 other corpses found a week later at three drug-gang “safe houses.” EFE