CIUDAD JUAREZ, Mexico — Ciudad Juarez's police chief stepped down Friday after criminal gangs made a chilling demand: Resign or we will kill more local officers.
Public Safety Secretary Roberto Orduna announced he was leaving his post only hours after gunmen killed a police officer and a jail guard and left signs on their bodies saying they had fulfilled a promise made Wednesday to slay at least one officer every 48 hours until Orduna quits.
The slayings were a sign that gangs are determined to control the police force of the biggest Mexican border city, with a population of 1.3 million people across from El Paso, Texas. Ciudad Juarez is a major entry point for drugs heading into the United States and a hot spot in a brutal, multi-front war involving ruthless drug cartels and Mexican security forces.
Ciudad Juarez Mayor Jose Reyes insisted earlier Friday the city would not back down.
"We will not allow the control of the police force to fall in the hands of criminal gangs," he said.
But Orduna said he didn't want to endanger more officers.
"We can't allow men who work defending our citizens to continue to lose their lives," he said. "That is why I am presenting my permanent resignation."
The resignation was effective immediately. Authorities said an interim chief would be named later Friday, and a permanent replacement would be found in the coming weeks.
A retired army major, Orduna took over as chief in May after former Public Safety Secretary Guillermo Prieto resigned and fled to El Paso following the slaying of his operations director.
For Orduna's protection, the city built his bedroom at the police station so he didn't have to go home. He also travels in different vehicles when he does go out.
Ciudad Juarez police have long come under attack, and many officers have quit out of fear for their lives, some after their names appeared on hit lists left in public throughout the city.
Police officer Cesar Ivan Portillo was the fifth officer killed this week in Mexico's deadliest city.
Police were placed on "red alert" _ meaning they could not patrol alone _ after cardboard signs with handwritten messages appeared taped to the doors and windows of businesses Wednesday, warning Orduna that one officer would be killed every two days if he did not quit.
That alert continued Friday after Orduna stepped down.
Police have also been asked to patrol with their guns in their hands.
More than 6,000 people have been killed in drug violence across Mexico over the past year as gangs battle each other for territory and fight off a nationwide crackdown by the army. Nearly a third of the slayings have taken place in Ciudad Juarez, and more than 50 of those dead are city police officers.
Violence also has spilled across the border into the U.S., where authorities report a spike in killings, kidnappings and home invasions connected to Mexico's murderous cartels.
Homeland Security officials have said they will bring in the military if the violence continues to grow and threatens the U.S. border region.
"The violence is spreading like wildfire across the Rio Grande," said George Grayson, a Mexico expert at the College of William & Mary in Virginia. "It's a major national security problem for us that is much more important than Iraq and Afghanistan."
Robert Almonte, executive director of the Texas Narcotics Officers Association, said that, while El Paso has been spared most of the violence, the escalating killings across the border in Juarez are worrisome.
"I think it's jarring ... we can't even fathom those kinds of things happening here in the United States," Almonte said.
Also Friday, the U.S. State Department renewed a travel advisory warning Americans about the increased violence along the U.S.-Mexico border.
Some Mexicans have questioned whether President Felipe Calderon's two-year, nationwide crackdown on drug gangs was worth all the killings.
But Calderon and his administration have defended the fight, with Economy Secretary Gerardo Ruiz Mateos saying on Wednesday that if Mexico gave up its fight against the cartels, "the next president of the republic would be a drug dealer."
Portillo and city jail guard Juan Pablo Ruiz were killed as they left their homes before dawn to head to work, city spokesman Jaime Torres said.
Three days earlier, assailants fatally shot police operations director Sacramento Perez, the chief's right-hand man, and three other officers who were sitting with him in a patrol car near the U.S. consulate.
Associated Press writers Marina Montemayor and Alicia Caldwell contributed to this story from Ciudad Juarez and El Paso, Texas.