Mexican police say gunmen have shot down the mayor-elect of a town in San Luis Potosi state and a campaign adviser while they were riding in a vehicle with another person.
The local public safety secretary said Matehuala Mayor-elect Edgar Morales Perez and aide Francisco Hernandez Colunga were returning from a birthday party when they were ambushed early on Sunday in the town.
Hernandez Colunga's wife was also in the car but survived the attack. The assailants remain at large.
A man who survived the attack with no injuries told police that unidentified assailants attacked the three men as they left a party.
San Luis Potosi has been rocked in recent days by a wave of violence attributed to drug cartels, including the discovery of 14 bodies inside a van on Thursday.
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Morales Perez had belonged to the Institutional Revolutionary Party, which regained the country's presidency last month.
He was scheduled to take office in September.
In a separate incident, the Mexico City Attorney General's Office confirmed that two people were killed by gunfire outside a bar in the capital and authorities found the missing head from a dismembered body discovered the day before.
A statement from the office said gunmen opened fire on 53-year-old Ruperto Acosta Diaz and 21-year-old Luis Alberto Segura Soto outside the bar Static in Iztapalapa early on Sunday morning, killing both men.
Acosta was a bouncer and Segura a singer at the bar.
The statement said Acosta had prevented two men from entering the bar the day before and they later returned and shot the bouncer.
On Saturday, a dismembered body was found in plastic bags in the southern district of Coyoacan. Authorities said they found the victim's head nearby on Sunday.
More than 50,000 people have been murdered since December 2006, when outgoing President Felipe Calderon launched a military offensive against drug cartels - whose failure analysts link to Calderon's defeat in the July polls.
Incoming President Pena Nieto has promised a "new strategy" and also pledged to wage his battle "without pacts or truces" a nod to the tactic his party was previously known for, of looking the other way while drugs were sent north of the border as long as the cartels did not commit violence within Mexico.
However, Nieto has yet to offer much detail of his plans.