MAZATLAN, Mexico (Reuters) - Relatives of 17 suspected gang members killed last week by police in northwest Mexico fear the death toll reflects a grim, repeated complaint in recent years - summary executions by security forces.

Joel Ernesto Soto, head of the Mazatlan municipal police, speaks during a news conference in Mazatlan, Mexico, July 3, 2017. REUTERS/Jesus Bustamante

The 17 men, who authorities said were armed with 24 guns, were killed by police near the coastal city of Mazatlan in the state of Sinaloa on Friday night. Another two people died nearby in what appeared to be related shootings, the state attorney general’s office said.

None of the suspects in the gun battle were found wounded or arrested.

Genaro Robles, Sinaloa’s head of police, attributed the outcome to better police training and said there was no excessive force or extrajudicial killing in the exchange. Five of 11 police officers suffered gunshot wounds. None died.

Relatives said the dead men were victims of a heavy-handed response by security forces that has stained Mexico’s human rights record.

Three relatives told Reuters they believed the victims were killed in cold blood. Two of them said their relatives had been shot in the back.

“They murdered them,” said the sister of one victim as she waited outside a funeral home in Mazatlan. She declined to give her name for fear of reprisals. “They didn’t have a chance. This wasn’t a gun battle, like they say in the news.”

Local municipal police rejected the allegation, though human rights officials were investigating possible abuses.

Mexican President Enrique Pena Nieto’s office referred questions to prosecutors in Sinaloa state and the federal attorney general’s office.

The federal attorney general’s office did not immediately respond to a request for comment, while the Sinaloa prosecutor’s office said it was not investigating any rights abuses, adding it could if human rights officials found evidence of wrongdoing.

Drug smugglers have been fighting for control in the state after a power vacuum emerged following the deportation of feared drug boss Joaquin “El Chapo” Guzman, a native of Sinaloa.

Police chief Robles said officers were alerted to two people injured behind a mall in the small town of Villa Union on Friday evening, and chased down the suspected assailants, sparking a gun battle.

Blood was visible on the road when a Reuters reporter visited the scene over the weekend.

Night-time footage later posted on social media, purporting to show victims, revealed bodies piled in the back of pickup trucks, with more scattered along a road. Reuters could not verify the authenticity of the videos.

The nephew of one victim said his uncle had worked for a drug cartel. “When I saw my uncle’s body it had gunshots in the back,” said the man, who also spoke on condition of anonymity.

One local policeman, who did not want to be identified, described the shootings as “butchery,” unlike other recent gun battles.

‘NOTHING UNTOWARD’

Miriam Hernandez of the Sinaloa state Commission for Human Rights said it had opened an investigation into whether the killings involved human rights abuses.

Joel Ernesto Soto, head of the municipal police in Mazatlan, whose men fought in the gun battle, welcomed the probe.

“They can come and ask and speak to us. We’ll be here waiting,” he said. “This event was completely fortuitous. There was nothing untoward.”

In 2015, police executed nearly two dozen suspected gang members in an ambush near the western town of Tanhuato, the national human rights commission found. It was one of the worst abuses by security forces in a decade of drug violence.

Police killed 17 people for every officer lost in gun battles in 2014, a university study found. The ratio was consistent with excessive use of force, experts said.

There were 619 murders in Sinaloa in the first five months of 2017, up more than 75 percent from 2016.

Family members gathered outside the Mazatlan funeral home said the violence was making police more corrupt.

“These killings were dirty,” said the mother of one victim, who declined to give her name. “This wasn’t a fight. It was something else, but what can you do?”