At least 19 gunmen have been reported killed and five police officers injured in a shootout with security forces in western Mexico.

The latest clash occurred on Friday evening when gunmen in four vehicles attacked 15 police officers in the town of Villa Union just south of the coastal town of Mazatlan in Sinaloa state. Marines and state police had gone to the aid of municipal police.

The police were on a routine patrol, led by local police chief Joel Ernesto Soto, when the gunmen attacked, according to Cristobal Castaneda of the state security department.

"They faced quite a number of aggressors, but thanks to their training and professionalism, they managed to get ahead. The wounded policemen are well," Castaneda told journalists.

State officials reported a 76 percent increase in homicides for the first five months of 2017 with more than 760 murders through early June - the highest figure in six years.

Gang-related violence throughout Mexico has escalated following the capture and extradition to the United States of former Sinaloa-based drug lord Joaquin "el Chapo" Guzman in January.

Sinaloa factions vying for power

A power struggle within the Sinaloa drug cartel has been blamed for the increase in violence since Guzman was extradited to the US. Considered by some to be the biggest drug lord of all time "El Chapo" is facing criminal charges related to his leadership of the Sinaloa cartel. Last week, one of his former mistresses, Lucero Sanchez Lopez, was arrested and then denied bail in San Diego as she faced charges of helping to launder money for the Sinaloa cartel and conspiracy to distribute cocaine. She is accused of facilitating communications between Guzman, the top tier of his cartel and the lower operatives.

Lopez is a former Sinaloa state legislator and was reportedly with Guzman when he escaped arrest in 2014 by escaping through a tunnel in his Sinaloa home hidden under a bathtub and leading to the city's sewers.

When leaders are taken out, groups tend to fragment or suffer from battles for leadership, according to commentators in Mexico.

Three factions are reported to be vying for control of the Sinaloa cartel: one led by a former state security official and Guzman's right-hand man, another led by two of Guzman's sons and the third by Guzman's brother who goes under the nickname of "El Guano."

Earlier this month, Castaneda said that the state did not have the resources it needed to fight the criminal groups running roughshod over the area. Insufficient police personnel, lack of training and competence were the main issues he cited. In Sinaloa state, more than half of police officers were reported to have failed integrity exams, according to government data published earlier this year.  

Diverse causes of violence

Violence has increased in other Mexican states, as well.  There were 2,186 murder investigations in Mexico in May, according to government statistics, making it the deadliest month since the country started to keep such records in 1997.  

Some of the violence may be due to increased cultivation of heroin to meet demand in the United States. 

Other factors include the legalization of marijuana in some US states which has knocked cartel profits from the drug trade and encouraged some gangs to turn to kidnap and extortion instead. 

Security forces have also been accused of a trigger-happy approach to dealing with the criminal gangs. The war on the cartels has been organized along military lines with police and security officers shooting first, leaving little time or opportunity for asking questions later.

The government-led crackdown on drug cartels and organized crime has been going on for more than a decade. An estimated 200,000 people have died and 30,000 disappeared. 

bik/jm (AFP, AP)