A shootout in Mexico near the US border among suspected drug traffickers and police left at least 21 dead, including four officers. According to authorities, te about whether the gangs should be deemed terrorists.

The incident started shortly before noon on Saturday in the northern state of Coahuila when officers detected several vehicles and heavily armed passengers touring the small community of Villa Union, 60 kilometers (40 miles) from the US border. The government of Coahuila state said 10 gunmen and four police were killed in the shootout in Villa Unión, days after US President Donald Trump fanned bilateral tensions by saying he would designate cartels as terrorists.

Shooting continued into early Sunday, the Coahuila state government said, adding that four of those killed were police, 14 were suspected criminals and another three bodies were unidentified. Six officers were wounded but their injuries were not serious.

Local authorities said three trucks were seized in the operation, as well as several high-caliber weapons and an unspecified load of ammunition. The shootout comes after Mexico’s leader Andres Manuel Lopez Obrador warned that he would not allow the US to conduct cross-border armed operations against drug cartels in the country.

US President Donald Trump has been talking tough on the cartels since one was allegedly responsible for the massacre of nine women and children from a US-Mexican Mormon community in northern Mexico on November 4. Trump said last week he plans to designate Mexican drug gangs as terrorist organizations.

According to The Guardian, The US attorney general, William Barr, is due to visit Mexico next week to discuss cooperation over security. US and Mexican criticism has focused on the armed forces’ release of a son of the drug lord Joaquin “El Chapo” Guzman under pressure from cartel gunmen in the city of Culiacán.