The bodies of 23 people have been found hanging from a bridge or decapitated and dumped near city hall in the Mexican border city of Nuevo Laredo, where drug cartels are fighting a bloody and escalating turf war. It follows the discovery in Veracruz of four journalists' bodies in a canal.

Authorities found nine of the victims, including four women, hanging from an overpass leading to a main highway, said a Tamaulipas state official who spoke on condition of anonymity.

Hours later police found 14 human heads inside coolers outside city hall along with a threatening note. The 14 bodies were found in black plastic bags inside a minivan abandoned near an international bridge, the official said.

The official provided no motive for the killings. But the city across the border from Laredo, Texas, has recently been torn by a renewed turf war between the Zetas cartel, a gang of former Mexican special forces soldiers, and the powerful Sinaloa cartel, which has joined forces with the Gulf cartel, former allies of the Zetas.

Local media published photos of the nine bloodied bodies, some with duct tape wrapped around their faces, hanging from the overpass along with a message threatening the Gulf cartel: "This is how I will finish all the fools you send."

It accused its rivals of setting off a car bomb that exploded outside Nuevo Laredo police headquarters last week and it made fun of a Sinaloa cartel enforcer killed in a Nuevo Laredo prison two years ago. "He cried like a woman giving birth," it said.

The interior secretary, Alejandro Poire, met with the Tamaulipas governor, Egidio Torre Cantu, on Friday and agreed to send more federal forces to the state, according to a statement from Poire's office.

Nuevo Laredo was the site of a 2003 dispute between the Sinaloa and Gulf cartels that set off a wave of violence that has left thousands dead and spread brutal violence that continues across Mexico until this day. That year, then-Gulf cartel leader Osiel Cardenas was arrested and accused drug lord Joaquin "El Chapo" Guzman, sensing weakness , tried to move in on Nuevo Laredo, unleashing a bloody battle.

The city of tree-covered plazas and hacienda-style restaurants was transformed as the Zetas, then working as enforcers for the Gulf cartel, and Sinaloa cartel fighters waged battles with guns and grenades in broad daylight.

Killings and police corruption became so brazen that then-president Vicente Fox was forced to send in hundreds of troops and federal agents. The only man brave enough to take the job of police chief was gunned down hours after he was sworn in.

The Zetas won that fight and have since ruled the city with fear, threatening police, reporters and city officials and extorting money from businesses. They broke off their alliance with the Gulf cartel in 2010, worsening the violence across north-east Mexico.

Last month 14 mutilated bodies were found in a vehicle left in the city centre, behind city hall. Some media outlets reported that the Sinaloa cartel took responsibility for those bodies and in a message allegedly signed by its leader, Guzman, declared that the group was back in Nuevo Laredo to "clean" the city.