Sept. 16 (Bloomberg) -- Eight people were killed and more than 100 injured after two grenades exploded last night at a Mexican Independence Day celebration in Michoacan state.

The attack occurred in the central square in the city of Morelia while state Governor Leonel Godoy was speaking to a crowd that gathered to hear him deliver the traditional Independence Day cry of ``Viva Mexico,'' said Jonathan Arredondo, head of communications for the state attorney general's office.

The perpetrators were most likely part of the drug gangs that plague the state, Godoy said in an interview with the Televisa network. Cartels have carried out a series of high- profile attacks in recent months in response to a crackdown ordered by President Felipe Calderon, including the dumping of 24 bodies in a park northwest of Mexico City last week and the decapitations of 12 men in Yucatan state last month.

``Calderon went after them, so they're hitting Calderon where it hurts,'' said Francisco Gonzalez, a professor of Latin American studies at Johns Hopkins University in Washington. ``They're trying to get civil society as scared as possible.''

Drug traffickers are trying to undermine the public's faith in security and reduce support for Calderon's anti-drug campaign, Gonzalez said.

`Cowardly Acts'

Calderon denounced the attacks as ``cowardly acts'' and urged Mexicans to set aside ideological differences and cooperate in the security effort.

Three people died immediately from the attacks, and five others succumbed later in hospitals, according to a Notimex news agency report carried by Televisa.

Thousands of Mexicans marched in more than 60 cities across the country last month, wearing white and carrying candles, to demand action from its government against rising bloodshed. More than 3,000 people have been killed this year in violence related to drug trafficking, according to figures compiled by local media.

The protests put pressure on Calderon, who took office in December 2006 promising to fight crime. Top police officers and civilians are being murdered as drug traffickers retaliate for arrests and record seizures stemming from Calderon's crackdown.

Mexican crime gangs are wealthy and well armed, mainly because of the profits from selling marijuana, cocaine, heroin and amphetamines to U.S. drug users. Many of the killings involve turf wars between cartels.

Hand-written signs hung from walls or highway overpasses threaten rival gang members or public officials, spreading terror among the populace. In the town of Creel, Chihuahua, last month, a dozen armed people broke into a dance hall and gunned down 13 people, including an infant.

To contact the reporter on this story: Hugh Collins in Mexico City at hcollins8@bloomberg.net

Last Updated: September 16, 2008 16:50 EDT