MEXICO CITY (Reuters) - Gunmen shot dead six traffic police in the central Mexican city of Salamanca on Friday, authorities said, one of the deadliest attacks on security forces in recent months.

The six were carrying out routine checks when they were killed, Guillermo Maldonado, a senior Salamanca city official, said in a video broadcast on Mexican television.

The motive for the daylight attack was not clear.

Broadcaster Televisa said at least three gunmen in a white vehicle opened fire on the unarmed victims, then fled the scene.

Homicides reached record levels last year in Mexico, and have climbed further this year, official data show.

Salamanca is home to one of state oil firm Pemex’s six refineries, which have been plagued by rising fuel theft and violence between rival criminal gangs.

Separately, the newspaper Reforma and broadcaster Milenio said that five people had been shot dead in the municipality of Leonardo Bravo in the violent southwestern state of Guerrero, according to state security spokesman Roberto Alvarez.

Reforma said the five were all members of one family.

Authorities in the state could not immediately be reached for comment.