Army troops and police searched for a group of about 50 gunmen who attacked a town in western Mexico over the weekend, killing four police officers and a civilian, officials said.
The gunmen attacked Vista Hermosa, a town in Michoacan state, on Saturday night.
Michoacan has been one of the states most affected by drug-related violence in recent years.
The attack occurred three days after authorities arrested Juan Garcia Garcia, the suspected boss of a gang that controlled the border area between Michoacan and Jalisco states.
The gunmen arrived in Vista Hermosa in an eight-vehicle convoy, a Michoacan Public Safety Secretariat spokesman told Efe.
The gunmen opened fire on a gas station with assault rifles, causing terrified motorists and pedestrians to flee.
The next target attacked was city hall in Vista Hermosa, a town of some 10,000 people, with the gunmen firing at least 2,000 rounds at the building.
Mayor Omar Corza Gallegos was meeting with the town council at the time the attack occurred.
Police chief Jose Luis Flores Martinez and a civilian standing outside city hall were killed.
Police officers from La Barca, a city in Jalisco state, responded to the attack in Vista Hermosa and three of them were killed by the gunmen, who had superior numbers and weapons.
The gunmen set fire to a patrol car and a civilian vehicle while making their getaway.
Michoacan Attorney General's Office investigators suspect that the attack may be linked to Garcia Garcia's arrest.
Garcia Garcia was arrested last Thursday by army troops in the nearby city of Yurecuaro.
The suspect was carrying four pistols, an assault rifle, military uniforms, synthetic drugs and a stolen SUV.
Michoacan has been plagued by a wave of violence blamed on the turf war between the Los Caballeros Templarios and La Familia Michoacana cartel.
Los Caballeros Templarios was created in March 2011 by former members of the La Familia Michoacana.
Servando Gomez Martinez shares the leadership of Los Caballeros Templarios with Enrique Plancarte.
Michoacan, which has more than 270 kilometers (168 miles) of Pacific coastline, has forests and mountain areas that provide perfect cover for drug production and smuggling.
Illegal drugs are smuggled from Central America into Michoacan and then later moved into the United States. EFE