Security footage of Thursday night's attack showed a group of at least five men entering the arena and opening fire with automatic rifles on a crowd of dozens in the rural community of La Valencia in northwest Ecuador.

The attackers were dressed in replica military uniforms -- a common tactic of criminal gangs in the country, which averaged a killing every hour at the start of the year as cartels vie for control over cocaine routes that pass through Ecuador's ports.

The footage, circulated on social media, showed spectators flinging themselves to the ground and taking cover under their seats.

"We have 12 people deceased as a result of an armed attack by a criminal group," police colonel Renan Miller Rivera said in a statement Friday.

He said several people were injured, without giving a number.

Police have detained four people, including a "target of intermediate value," national police chief Victor Hugo Zarate wrote on the X social platform.

After the attack, police found discarded "military-style uniforms" and two abandoned cars on a nearby highway, Miller Rivera added. One of the cars had been set on fire, the other had overturned.

Ecuador is home to around 20 criminal gangs involved in trafficking, kidnapping and extortion. They have wreaked havoc in the country of 18 million squeezed between the world's biggest cocaine producers, Peru and Colombia.

In recent years, the nation has been plunged into violence by the rapid spread of transnational cartels that use its ports to ship drugs to the United States and Europe.

About 73 percent of the world's cocaine passes through Ecuador, according to an interior ministry report.

Large parts of the country are under a state of emergency recently renewed by President Daniel Noboa, who was re-elected to a second term in elections last Sunday.

On the campaign trail, he suggested US special forces should be deployed to Ecuador to tackle drug violence and floated legal reforms to allow US bases to operate in the country.