|The latest killings are among over 36,000 in Mexico since 2006 [EPA]
At least 22 people have been killed in a string of weekend attacks in Mexico, including a shooting at a bar in Monterrey, the country's third largest city, just hours after the nearby opening of football's Under-17 World Cup.
Four people, aged 18 to 25 years old, were killed on Sunday in Guadalupe, a city adjacent to Monterrey.
"The victims were gathering in front of one of their homes when armed men showed up in several vehicles and shot them," an official said.
Another 14 people were killed in the western state of Michoacan, whose bodies were found early on Sunday, authorities said, also blaming drug cartel-related violence there.
Gunmen stormed a bar in Monterrey late on Saturday and "executed three people," wounded another, and kidnapped a bar security guard who was later found dead, an official of Nuevo Leon state's investigation agency told the AFP news agency.
The relatively prosperous industrial hub of northern Mexico, home to Monterrey and Guadalupe, was until recently considered a near-safe haven as violence has increased in many parts of the country.
But a bloody turf war between two drug cartels, the Gulf cartel and its former hitmen the Zetas, has spilled into the state over the past two years, leading to daytime shootouts, grenade attacks and a widespread climate of fear.
Thirty-three violent killings were recorded in and around Monterrey, an area of some four million, on Wednesday, making it the area's most violent day in recent history.
'Climate of impunity'
John Gibler, an investigative journalist and author of To Die in Mexico, says that blaming violence on drug-related crime is an easy excuse for the government, where "cops are actually or tangentially involved" in trafficking and violent crime.
"The violence in the border regions does have to do with the trafficking organisations - and those organisations are all connected to various levels of government on both sides of the border, [but] that battle itself, inside the logic of [drug] prohibition, sets off all other sorts of violence," Gibler said in an interview with Al Jazeera.
"When you have a place like Mexico, where five per cent of all murders are investigated, it creates a climate of impunity where people simply feel like it's easy to get away with murder."
Mexico is in the grip of a brutal wave of violence that has killed about 37,000 people since Felipe Calderon, the president, launched a military crackdown on organised crime in 2006.