Suspected drug cartel "hit teams" gunned down an American consular employee and her husband in a Mexican border city and killed a co-worker's Mexican husband in a separate attack, a US official said Sunday.
The victims -- two Americans and a Mexican -- came under fire in separate locations as they were driving Saturday through Ciudad Juarez after earlier attending the same social event, the official said, speaking on condition of anonymity.
The killings marked an ominous turn in the drug violence wracking northern Mexico, and prompted the State Department to announce that Americans working at six US consulates in the border area could send their families away.
President Barack Obama said he was "deeply saddened and outraged by the news of the brutal murders," said National Security Council spokesman Mike Hammer.
The victims came under fire in separate locations after attending the same social event earlier in the day, the US official said, speaking on condition of anonymity.
"Suspected drug cartel hit teams fired on locally employed staff, Consulate General Juarez, in their privately owned vehicles," the official said.
"The attacks resulted in three fatalities -- two American citizens and one Mexican citizen," he said.
The victims included a US woman employed by the consulate's American citizens services section who was with her American husband and infant daughter when they came under fire, the official said.
The infant, who was in the back seat, survived the attack unharmed, but the woman and her husband were killed, he said.
In the second attack, a Mexican employee of the consulate was following her husband and two children in a separate car, when her husband's vehicle came under fire, killing him and wounding the two children, the official said.
"Both families had attended the same social event earlier in the afternoon off-post away from the consulate," the US official said. "It has not been determined if the victims were specifically targeted."
Shortly after the killings were disclosed by the White House, the State Department issued a travel warning for Mexico.
It said Americans working in consulates in the northern cities of Tijuana, Nogales, Ciudad Juarez, Nuevo Laredo, Monterrey and Matamoros were authorized to send family members home until April 12 because of security concerns.
The departure authorization only affect relatives of US government personnel in those cities, the statement said.
The travel warning said that due to the "recent violent attacks," US citizens were urged to "delay unnecessary travel to parts of Durango, Coahuila and Chihuahua states."
"While millions of US citizens safely visit Mexico each year ... violence in the country has increased," the State Department said.
"Drug cartels and associated criminal elements have retaliated violently against individuals who speak out against them or whom they otherwise view as a threat to their organizations," it read.
The State Department travel warning was issued "coupled with the increase of violence in that northern area," said Department spokesman Fred Lash.
"It's not an ordered departure, it's up to them if they want to come out or not," said Lash told AFP.
Ciudad Juarez, population 1.3 million, is a major hub for smuggling illegal drugs into the United States. It is directly across the border from El Paso, Texas.
More than 2,600 people were murdered in Ciudad Juarez in 2009 in drug-related violence.
The war between rival drug cartels to control major border crossing points, as well as the government's attempt to crackdown on the cartels, has killed more than 15,000 people across Mexico over the last three years, according to government figures.
The State Department warning said that some of the recent clashes "have resembled small-unit combat, with cartels employing automatic weapons and grenades."
"Large firefights have taken place in towns and cities across Mexico, but occur mostly in northern Mexico," the statement read. "During some of these incidents, US citizens have been trapped and temporarily prevented from leaving the area."
More than 60 people were killed over the weekend in Mexico, including 38 in the southern state of Guerrero, Mexican officials said.