The recent murder of a couple and their three children in the western crime-plagued Mexican state of Michoacán took the number of families massacred in Mexico in the past two weeks to five.

It came after two families were slain on the other side of the country, in the northeastern border state of Tamaulipas. Gunmen stormed a family home and killed 11 people, including four young girls. In another attack, hitmen murdered two women and three children, also in their home.

The wave of family-focused violence has also hit the normally less-violent southern state of Oaxaca.

Eight members of a single family that included several shark fishermen were killed in the city of Puerto Escondido, known for its tourism, beaches, and fishing. Days later, hitmen gunned down a couple and their son in the city of Juchitan, leaving behind a letter that claimed the murders were related to criminal activities.

According to a count by Mexican daily El Universal 24 families have been murdered in 2016.

The wave of massacres comes in the context of a jump in homicides. Official statistics released last week showed the number of murders in the first six months of the year at their highest level since 2012. The figures also chart increases in murder rates around the country so that the violence is now less concentrated in certain states where turf wars between cartels are particularly intense.

There is no obvious reason for the recent targeting of whole families, which have taken place in different parts of the country where different criminal groups are fighting each other.

However, Mexico's drug war violence has regularly displayed particular trends within the horror. These include the posting on the internet of videos showing beheadings and torture, and hanging the bodies of victims from highway overpasses.

"Organized crime violence is often stylized," said Howard Campbell, chairman of the anthropology department at University of Texas El Paso and the author of a book on violence in Mexico. "These incidents seem to perpetuate themselves and you have this copycat phenomenon."

Campbell said that the current focus on eliminating whole families was particularly painful in Mexico.

"Much more than the United States, which is an atomized country, Mexicans see themselves as part of groups, especially family groups," he said. "If you want to attack someone or harm them, the worst thing you can do to them is murder their family."

The rising violence is not just seen in the number of family massacres.

Two mayors were felled by gunfire over the weekend — one in the beleaguered state of Guerrero and the other in the southern state of Chiapas.

Ambrosio Soto Duarte, the mayor of Pungarabato in Guerrero, died as his bodyguards repelled an attack on his vehicle in the neighboring state of Michoacán. Authorities found hundreds of bullet shells at the scene.

Soto Duarte tweeted that he was in danger and appealed for help from President Enrique Peña Nieto just weeks before.

"They killed my brother, I am being threatened by organized crime. Now it is time to act, Mr. President," the tweet said. "Tierra Caliente needs you."

He was referring to the rural region where he was killed that links Guerrero and Michoacán, and where many different criminal organizations operate and battle for territory.

The same day, a protest over public resources in the indigenous town of San Juan Chamula in Chiapas ended with the death of Mayor Domingo López González and four others, including his second in command. The mayor had been talking to the protesters when the shooting began.

The National Association of Mayors released a statement on Sunday asking the government to create a system to provide better security for elected officials. The group said that 40 mayors, seven electees, and 32 ex-mayors have been murdered around the country since 2006.