Los Tiguerones, which has been linked and other illicit activity, funds criminal activity against law enforcement and civilians, according to Rubio.
"Los Tiguerones is yet another Ecuadorian gang helping Mexican cartels move and export illicit drugs to fund terrorism and criminal activity including attacks against civilians, law enforcement, and journalists," Rubio said in a post on X.
Rubio added that the group was responsible for the live takeover of an Ecuadorian television station in 2024.
The decision comes on the heels of the designation of three other groups, including Los Lobos and Los Choneros, in July.
"They're not ordinary. These are violent, bloodthirsty terrorist organizations. And we have to make sure that we continue to pursue them," Rubio said.
The announcement was made while Rubio was visiting Quito, Ecuador, as part of a three-nation tour to strengthen economic and security ties with Peru, Ecuador and Colombia.