Police early Thursday found the body of a 4-year-old girl who had been shot in the chest _ the fifth child killed in drug-related violence in this Mexican resort city in less than a week.

The child was in a car next to a woman who had been shot three times in the back, Guerrero state police said in a statement. Police did not release the identities of the victims or discuss a possible motive for their slayings.

At least five young people have died in drug violence in Acapulco since Sunday, including a 2-year-old boy and a 6-year-old boy killed with an elderly woman who tried to shield them when gunmen opened fire at their home.

Police found more than 200 shell casings at the scene in a poor neighborhood in Acapulco, which has been the scene of bloody drug cartel turf battles. Witnesses told police a man being chased ran inside the house minutes before gunmen started shooting. It was not clear what happened to the man.

That same day two 15-year-olds were killed in separate attacks.

Children and youths have increasingly been targeted in killings or died as bystanders caught up in Mexico's drug war, which has resulted in more than 35,000 deaths since December 2006, when President Felipe Calderon took office and launched a stepped-up offensive against cartels.

Also Thursday, police found the bullet-ridden body of a man outside a state prison in Acapulco. A threatening note was found next to the body. Authorities did not disclose its content.

Guerrero state has seen a spike in violence since rival factions of the Beltran Leyva cartel began fighting over territory following the December 2009 death of capo Arturo Beltran Leyva.

In the adjoining state of Michoacan, police found two bodies hanging from the neck in two different towns Thursday. Both had a threatening note with the same message signed by a purported new drug gang, state prosecutors said.

Police first found a badly bruised body in the town of Lagunillas, near the state capital of Morelia, along with a message reading: "We killed him for being a thief and a kidnapper."

Prosecutors said it was signed "Knights Templar" _ a little known gang that announced itself as the replacement for the weakened La Familia drug cartel last week in banners hung throughout Michoacan.

The second body, which had bullet wounds, was found in the town of Mujica.

In another Pacific coast state, marines found the bodies of two men and two women buried in two clandestine graves in the state of Jalisco, the Navy said in a statement.

One of the bodies belonged to Saul Adame Barreto, who was the chief of staff for Colima state Gov. Mario Anguiano and who disappeared Feb. 23, the Navy said.

It said an alleged member of a drug cartel detained in the neighboring state of Jalisco led them to the graves. The other three victims have not been identified, it said.

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Associated Press writer Gustavo Ruiz in Morelia, Michoacan, and Olga R. Rodriguez in Mexico City contributed to this report.