Noe Morales, the local police spokesman, said four men and three women died when unidentified assailants sprayed bullets into a wedding party in the village of Zacualpan, Guerrero state.
He said the assailants escaped and their motive was unknown.
Separately, police in the neighbouring state of Michoacan, where the Mexican president is cracking down on drug gangs, dug up the bodies of two men in their early 30s who had been killed and dumped in shallow graves at a farm up to four weeks earlier.
The men's feet and hands were bound and their mouths taped over. One wore a face-covering hood and had tape over his eyes.
"The attorney-general's office is working out whether it's linked to drug trafficking," said Magdalena Guzman, spokeswoman for the state prosecutor.
Also on Sunday, residents in the impoverished town of Ecatepec, just north of Mexico City, led police to an abandoned car containing the bodies of three men, about 30 years of age, local media reported.
Once limited mainly to northern border cities, violence surged and spread south after the former president, Vicente Fox, launched a crackdown on drug gangs in early 2005, intensifying the turf war between the Gulf Cartel from northeastern Mexico and smugglers from Sinaloa and Tijuana in the northwest.
Days after he was sworn in on December 1, Calderon sent 7,000 soldiers and police to his home state of Michoacan, which is overrun by gangs jostling for lucrative routes to smuggle cocaine, marijuana and methamphetamines to the United States.
Calderon also announced the creation of an elite force made up of thousands of soldiers and federal police to chase down drug cartels, kidnappers and other organised crime.
Mexico's municipal and state police, poorly paid and badly equipped, are widely perceived as inept and highly corrupt.