Four soldiers were killed and nine injured when their military patrol came under attack with explosives while tracking down a criminal group in western Mexico, President Andres Manuel Lopez Obrador said Friday.

The ambush took place Thursday in a rural area of the Aguililla municipality in Michoacan province, the president said at his daily press conference.

The soldiers had stumbled upon a trap, an explosive that killed one soldier on the spot and fatally wounded three more, said Lopez Obrador. Nine others were injured.

This is what the Army, the Marine Corps and the National Guard have to face, said the president, who faces frequent criticism from the opposition demanding a heavier hand against the countrys powerful drug cartels.

Lopez Obrador prefers a strategy he calls hugs not bullets to tackle the causes of violent crime, such as poverty and inequality rather than military force.

Mexico has registered more than 420,000 murders and 110,000 disappearances - most attributed to criminal groups - since the launch of a controversial military anti-drug offensive in 2006 by then-president Felipe Calderon.

Military sources consulted by AFP in Michoacan said anti-personnel mines and drones with explosives were used in Thursdays ambush.

The area where the attack occurred is the scene of a dispute between the Jalisco New Generation Cartel and another organization known as El Abuelo.

News of the latest attack came on the same day Mexico launched campaigning for the presidential election, with two women - Claudia Shainbaum and Xochitl Galvez - in the lead in a nation with a long tradition of macho culture. (AFP)