The second politician murdered within a week, Alejandro Chavez Zavala's death brings the total number of candidates killed since September to 114.

Mexican mayoral candidate Alejandro Chavez Zavala was gunned down after a campaign event Thursday afternoon in La Florida, Taretan, as the political violence plaguing the nation continued to escalate ahead of the elections.

Chavez and his wife, Mary Dimas, were shot by an unknown assailant driving a black Ford Lobo while leaving the city following a campaign event.

The couple was transferred to the Regional Hospital of Uruapan and Dimas initially in a stable condition, but the National Action Party (PAN) representative had sustained several bullet wounds which damaged multiple vital organs and he died within minutes.

The killing was condemned by his colleagues and running mates. Governor Silvano Aureoles of Michoacan offered his condolences and said investigations are already underway.

"I deeply regret the death of Alejandro Chavez Zavala, candidate for mayor of Tareta...We will not rest until we find those responsible for these reprehensible acts, where his wife was also injured. No act that threatens the integrity of the Michoacan must go unpunished," Silvano posted on his Twitter account.

Michoacan police tweeted: "In Taretan we implemented a search operation to find those responsible for events that occurred on Thursday, where Alejandro Chavez Zavala, a municipal president with license and candidate for re-election, was injured."

At least 113 politicians have been killed in the bloodiest election campaign in Mexico's modern history, and the violence appears to be intensifying in the final weeks before the July 1 national election.

According to Mexico City-based security consultancy Etellekt, many of the slain candidates were running for local office.

Michael Lettieri, a historian at the Center for U.S.-Mexican Studies at the University of California, San Diego, said: "The risk going forward is that there will be reluctance to participate in local politics because it has become so dangerous."

Political assassinations have rocked the electoral season leading up to July 1, when voters will decide 3,000 down-ballot seats and elect a new national president.