Venezuelan opposition leader Juan Guaidó rejected allegations on Friday that he has ties to an illegal armed group in Colombia, as officials launched an investigation based on photos appearing in social media purportedly showing him posing with members of the gang.

The pictures were allegedly taken in late February when Guaido crossed into Colombia and made a surprise appearance at a concert organised by billionaire Richard Branson aimed at helping deliver humanitarian aid to Venezuela.

Government officials loyal to President Nicolas Maduro are holding up the photos as proof that Guaido’s covert journey was orchestrated with the help of a Colombian criminal gang known as the Rastrojos, an accusation he denies.

“That day I took photos with many people,” Guaido told Colombia’s BLU radio.

“Evidently it’s hard to know who is asking you for a photo.”

The spat over the pictures comes amid escalating tensions between Colombia and Venezuela as the presidents of both countries accuse one another of harbouring illegal armed groups plotting across-the-border attacks.

On Wednesday, a dozen nations including the United States invoked the Inter-American Treaty of Reciprocal Assistance, which contends that a threat against any single signatory should be considered a danger to them all. The act raises the stakes of a potential military response though all sides have said they want a peaceful solution.

Venezuelan Interior Minister Nestor Reverol appeared on state television Friday laying out evidence for a new probe into Guaidó, displaying images at the center of the controversy.

“They prove yet again Guaido’s association with all the terrorist actions being planned in Venezuela to disrupt the stability and peace of our democracy,” he said.

General Luis Fernando Navarro, the commander of Colombia’s military, said two of the men seen in the photos with Guaido are members of the Rastrojos who have now been captured. The photos show both men posing individually with Guaido before a wooded background.

Navarro identified one of the men as Albeiro Lobo Quintero, alias Brother, and the other as Jhon Jairo Durán, alias Menor. Quintero allegedly turned himself into Colombian authorities sometime after the photograph was taken, while Duran was captured from a canoe after being injured in a fight with another criminal group in Venezuela.

Navarro said he couldn’t confirm exactly when or where the photos were taken.

Guaidó told BLU radio that he had no recollection of the photos being taken, and that he is pleased to know both men are no longer free.

“I celebrate that they’ve been detained,” Guaido said.

The Rastrojos have been operating in the region for nearly two decades and at one point were considered a major drug trafficking group. However, their numbers are believed to have waned after the capture of several top leaders in 2012.

Tarek William Saab, Venezuela’s attorney general and a Maduro ally, rejected Guaido’s claim that he had no idea who the men were.

The new investigation is the fifth that Venezuelan officials have launched against Guaidó in recent months. He’s also being accused of sparking violent protests and orchestrating a nationwide blackout.

A video released back in February showed Guaido crossing a small border bridge with a dozen aides dressed in collared work shirts. He jogged as he crossed, lifting up his hand and shouting encouraging words like, “We can do it!”

Colombian President Iván Duque said Friday that officials had helped Guaido in securing his safety as he entered the country though provided few details.

“We facilitated his entry to Colombian territory,” he said.

Meanwhile, Foreign Minister Jorge Arreaza said on Friday that Venezuela is “ready” to defend itself, after Washington invoked a regional defence pact that might justify such a move.

“We are ready to protect ourselves, we are ready to react,” Arreaza told a news conference after meeting in Geneva with UN rights chief Michelle Bachelet.

Agencies