At least six Colombian soldiers have been killed in a bombing in the country’s northwest, the army said, attributing the attack to accused drug traffickers who are active in the area.

Another five soldiers were injured and one remains missing after the attack, which took place around midnight Tuesday in the Antioquia department and was blamed on the Gulf Clan cartel.

“Unfortunately the murder of six of our soldiers is confirmed,” the army said in a statement on Wednesday.

The five injured soldiers from the Fourth Brigade “were evacuated by aeroplane” to a hospital.

“Troops on the ground are continuing to look for one of our soldiers,” the army said.

Authorities in the South American nation captured the head of the Gulf Clan cartel, Dairo Antonio Usuga in October of last year. Better known as Otoniel, he was Colombia’s most-wanted drug trafficker.

Otoniel was captured by Colombian forces in October 2021

Colombia is the world’s biggest producer of cocaine, according to the United Nations Office on Drugs and Crime (UNODC).

President Ivan Duque welcomed Otoniel’s arrest as “the biggest blow to drug trafficking” in the country in decades.

Duque has said his government is working to extradite him, most likely to the United States, where he is wanted on drug trafficking charges.

The Gulf Clan has increased its attacks in the aftermath of Otoniel’s capture.

General Juvenal Diaz told Blu Radio that the group was responsible for Tuesday’s attack, in which “an improvised explosive device” was detonated as a military vehicle was passing.

Authorities said that the Antioquia department is a main corridor for the transportation of cocaine from Colombia’s Pacific coast towards Panama and the US.

The attack comes as the country is preparing for elections next month.