Ecuadorian President Lenin Moreno has said that the three journalists abducted last month near the Colombian border are dead.
From Peru, President Martin Vizcarra said: "Our solidarity with President Lenin Moreno, the families and the Ecuadorean people for the awful murder of the three Ecuadorean journalists".
Ecuadoran experts examined the photos but were unable to confirm their authenticity.
As Moreno spoke, dozens of colleagues and friends of reporter Javier Ortega, photographer Paul Rivas and their driver Efrain Segarra gathered in tears in a plaza outside the presidential palace under the slogan "Three Are Missing", the same one that has featured in candlelight vigils held nearly every night since their disappearance.
Moreno also announced that operations resumed on the border with Colombia and offered a reward for what he called the "narco-terrorist, alias Guacho", leader of the group that kidnapped and murdered El Comercio's news crew.
Moreno was already in Lima when the photographs emerged, prompting him to urgently return to Quito to handle the crisis.
The murders drew a swift condemnation from Colombian President Juan Manuel Santos, who slammed "a deplorable act".
Ecuador's Communications Minister Andres Michelena said the delegation would be involved in preparing "joint operations", without giving further details.
On April 3, Colombia's RCN television aired a 23-second video showing the trio wearing chains with locks around their necks, in what was the first proof of life.
He stressed that "beyond the efforts we have made, it has been confirmed that these criminals appear to never have had the will to deliver them safe and sound, and it is very likely that all what they wanted was to buy time".
While more than a dozen journalists used to be killed every year in Colombia at the height of Pablo Escobar's reign in the late 1980s and early 1990s, the numbers have fallen dramatically as the country's half-century conflict winds down to that point only a single press worker was killed in 2017, according to the New York-based Committee to Protect Journalists.
The team was abducted while on assignment along the common border, where Ecuadoran security forces have come under attack by ex-FARC groups who still engage in drug trafficking.
One of the hostages appealed to Moreno help secure their release.
The region has always been a hotbed for Colombian drug traffickers and rebel groups (which are often the same), and has been the setting for a string of recent attacks against military targets.
Frente Olive Sinisterra, the organization responsible for the kidnappings, is described by the Colombian government as a splinter group from the former Revolutionary Armed Forces of Colombia (FARC).
However, some 1,100 guerrillas broke away from the agreement, primarily to pursue drug trafficking and illegal mining, according to the Colombian government and independent research centers.