MEXICO CITY (Reuters) - Mexican federal troops killed eight alleged gang members on Wednesday in battles along a highway near the U.S. border in the northern state of Tamaulipas, a region plagued by a bloody dispute between drug cartels.
The gunmen were killed in separate battles after they hijacked buses and used them to block a highway between the cities of Matamoros and Reynosa, opposite the Texas border towns of Brownsville and McAllen, a federal and state police task force said.
An explosive device was also found and deactivated in front of the mayor's office in Matamoros, the task force added.
Residents rely on reports from social media to learn about frequent gun battles, which can rage for hours.
Local media, which have been repeatedly attacked by the gangs, refrain from reporting the violence.
The U.S. consulate in Matamoros issued a statement on Wednesday warning American citizens of the spike in violence, which it said had been attributed to a battle between Matamoros and Reynosa factions of the Gulf Cartel.
The consulate said staff had been advised to restrict travel in the city, noting that there had been a surge in violence and an increase in reports of large convoys of armed drug gang members driving through Matamoros.
"While daytime convoys of armed Transnational Criminal Organization members are not necessarily unusual for Matamoros, the amount of violence that has resulted from gun battles between these rival factions is cause for increased vigilance," the consulate said in a statement on its website.
Besides trafficking illegal drugs, the gangs also kidnap and extort money from Central American immigrants seeking to enter the United States illegally. In 2010 and 2011 the Zetas were linked to massacres of migrants fleeing poverty and violence in their own countries.
Tamaulipas state led the country in kidnappings in 2014, with 264 cases compared with 211 in 2013. Homicides rose to 628 in 2014 compared with 555 in the previous year, according to federal data.
Reporting by Anahi Rama and Lizbeth Diaz. Editing by Andre Grenon and Ken Wills