Seven people were hurt Friday when a car bomb detonated in front of city hall in the border city of Nuevo Laredo, authorities in the northern Mexican state of Tamaulipas said.

The explosion occurred at 11:15 a.m. and all of the injured were civilians, the state government said in a statement.

The city hall, nearby businesses and 11 vehicles were damaged in the blast.

The explosives-laden car was just a few meters (yards) from Mayor Benjamin Galvan's parking spot and his whereabouts at the time of the attack remain unknown.

Federal police and troops cordoned off the crime scene as paramedics stabilized the injured for transport to hospitals.

The attack comes less than 48 hours before Mexicans go to the polls on Sunday to elect a new president and fill more than 2,000 other public posts.

Nuevo Laredo, just across the border from Laredo, Texas, has been wracked by a brutal struggle between the Sinaloa and Los Zetas drug cartels for control of smuggling routes into the United States.

More than a year ago, the Mexican army replaced municipal police on the streets of Nuevo Laredo amid concerns that many local cops were on cartel payrolls. EFE