The death toll from two days of gunfights in Mexico's northern state of Tamaulipas rose to 24 on Monday after authorities reported six more slayings in the drug violence-plagued region.
Authorities said 15 men and two women were killed on Sunday in a series of shootings between criminal groups in the towns of Tampico and Ciudad Madero, on the Gulf of Mexico coast.
A man's body wad found on a bench and two others on a street in Tampico early Monday, according to the Tamaulipas Coordination Group of federal and state security forces.
The first shootout was reported in Ciudad Madero, where two gunmen killed two men and a woman on Sunday afternoon, the security group said in a statement.
Ten minutes later, authorities in neighboring Tampico found the body of a man with a bullet wound to the head.
Later, a carload of gunmen fired at a man whose body was found in a Ciudad Madero street. Ten minutes later, another body was found in a street corner of the town.
After nightfall, five men and one woman were killed in front of a fuel station in Tampico. Moments later, another man was gunned down in an ice cream shop.
Another body was recovered that evening in Madero.
The statement did not say what gangs were involved in the killings.
But Tampico Mayor Gustavo Torres told Milenio television that the shootings in his town were linked to "score-settling" between members of the Gulf Cartel.
Tamaulipas has been the scene of a turf war between the Zetas and Gulf drug cartels, former allies that have battled for control of lucrative drug trafficking routes to the United States since they parted ways in 2010.
The Tamaulipas Coordination Group said in a separate statement that four suspected criminals were detained Sunday in two Tampico homes, armed with rifles and grenades.
Further north, three more people were killed Sunday in clashes between criminals near the Rio Grande in Ciudad Mier, which lies near the border with the US state of Texas. Those killings were also reported on Monday.
Soldiers recovered a pick-up truck, three AK-47 and one AR-15 assault rifle, one grenade and two bulletproof vests.
The bloody Sunday came one day after a gun battle between soldiers and suspected criminals in Ciudad Miguel Aleman, which is near Ciudad Mier.
Four armed civilians were killed in a skirmish after they opened fire on a hotel, the state prosecutor's office said.
Some 80,000 people have been killed in drug violence in Mexico since 2006.