By Stephen Gibbs
BBC News, Mexico City
About 5,000 people are said to have died in drug violence this year
It has been another violent weekend in Mexico's drug wars.
Ten suspected traffickers and a soldier were killed in a shootout on Sunday in the southern state of Guerrero.
Another six people were killed in the north of the country when gunmen opened fire inside a pool hall in Ciudad Juarez, on the US-Mexico border.
The Mexican defence department also said that at least eight bodies had been found in a shallow grave in central Michoacan State.
At dawn on Sunday morning in the normally quiet town of Arcelia, residents were woken by the sound of a major gun battle.
Initially it appears to have been between rival heavily armed drug gangs in a fleet of cars. Later the police and army joined in. By the time it all ended, 11 people, including one soldier were dead.
The confrontation exemplifies what many observers say is behind the violence that is spiralling in Mexico.
Two years ago, President Felipe Calderon launched an all-out assault on the country's drug cartels, which for many years had operated with minimal government interference.
Under pressure for their lucrative routes, the traffickers are fighting both among themselves, and against federal forces.
The brutality of this war is shocking Mexico. Every day, the papers contain vivid images of another killing.
Also on Sunday, Ciudad Juarez, focus of much of the recent violence, provided yet another headline.
Armed men drew their weapons inside a billiards hall, murdering six people. And in Michoacan State, west of Mexico City, soldiers uncovered a shallow grave, with the remains of at least eight bodies. The corpses had been cut in pieces and burned.
President Calderon is facing some pressure from those who wonder whether the war against the cartels is winnable.
He has repeatedly stated his conviction that unless the traffickers are defeated, Mexico's future as a viable country is uncertain.