The six people who have been arrested in connection with the killing of Ecuadorian presidential candidate Fernando Villavicencio are Colombian, police say.
A seventh suspect, who died from wounds in a shootout with police on Thursday, was also Colombian.
Mr Villavicencio was killed leaving a campaign event in the capital Quito.
The interior minister said a police investigation into the “abominable event” was under way.
Interior Minister Juan Zapata said officers would work to “discover the motive of this crime and its intellectual authors”.
The six detainees have been identified as Andres M, Jose N, Eddy G, Camilo R, Jules C, and Jhon Rodriguez, Mr Zapata told a press conference on Thursday.
He added that during the police raid that resulted in their arrest, officers found a rifle, a submachine gun, four pistols, three grenades, four boxes of ammunition, two motorbikes, and a vehicle that had been reported stolen in the group’s possession.
A vocal critic of organized crime, Mr Villavicencio was one of the few presidential candidates to allege links between corruption and government officials.
President Guillermo Lasso said the assassination was an attempt to sabotage the election.
He added that voting would go ahead as planned on 20 August, despite a national state of emergency.
He said organised crime was behind the killing and has asked US federal agents to help investigate, with FBI agents due to arrive shortly.
Mr Villavicencio, a member of the country’s national assembly, had received threats from a gang calling itself Los Choneros last month and had been given a security detail.
Following his murder, a video appeared on social media in which heavily armed men wearing balaclavas claimed responsibility for the murder. The men claimed to belong to Los Lobos (The Wolves), who are rivals of Los Choneros.
However another video appeared online just hours later, in which another group of men – this time not wearing masks – claimed they were Los Lobos members and denied any role in the assassination, claiming the other video was an attempt by their rivals to set them up for the murder.