Venezuela appears to have sent two foreign members of Ukraine’s military last month to face trial in Moscow, a significant escalation of the Kremlin’s campaign to punish its enemies abroad.

The arrest of Colombian fighters in Moscow followed their arrival and subsequent disappearance in August in Venezuela, a neighbor of Colombia and a Russia ally.

Their apparent extradition could damage relations between the governments of Venezuela and Colombia, which share close economic and historical ties, experts said, underlining how the war in Ukraine is creating geopolitical ripples far from the battlefield.

Russian state media on Friday published a video of the country’s secret police interrogating the two Colombians, José Medina and Alejandro Ante, about their combat service in Ukraine, where they fought in the ranks of the Ukrainian armed forces for eight to 10 months.

A Moscow court on Aug. 29 separately ordered Medina and Ante taken into custody on accusations of being mercenaries, a crime under Russian and international law.

Relatives of the two Colombian service members confirmed to The New York Times that the men seen in the video being hauled through a corridor by security officers and later interrogated were Medina and Ante.

The relatives said they last heard from the two men, retired Colombian professional soldiers, July 18 when they landed in Caracas, the Venezuelan capital, as they traveled home from the battlefields of Ukraine.

“Hey my cutie, heading to Venezuela, and soon to Colombia,” Medina, 37, said in a video sent to his wife, Cielo Paz, as he walked in his military uniform toward an airplane that would take him from Madrid to Caracas. Medina later shared his geolocation in Caracas’ international airport, Paz’s phone records show, before breaking off contact.

Venezuela’s government has not commented on the apparent detention and extradition of the Colombians. The country’s Foreign Ministry did not respond to a request for comment.

Venezuela’s government has also not responded to official requests made in the past month by Colombia for information about Medina and Ante’s whereabouts, according to copies of two diplomatic letters seen by The New York Times.

Venezuela’s president, Nicolás Maduro, has long allied himself with Russia in his standoff with the United States over his government’s authoritarian turn.

But he has also attempted to maintain good relations with Colombia’s leftist president, Gustavo Petro, an ideological peer of Venezuela’s nominally socialist government.

Venezuela’s apparent extradition of two Colombian citizens comes at a particularly sensitive time for Maduro’s relations with Petro, who is attempting to mediate a political agreement between the Venezuelan government and the opposition following a contested presidential election there in July.

Venezuela’s electoral body proclaimed Maduro the winner without providing any details, while vote counts from electoral observers released by the opposition show that he lost decisively.

In approving the apparent extradition of Colombian citizens, Venezuela’s government is showing that Maduro is prioritizing traditional alliances with authoritarian nations such as Russia at the expense of more neutral democracies such as Colombia as he hunkers down, said Vladimir Rouvinski, an expert on Latin American relations with Russia at the Icesi University in Cali, Colombia.

“Maduro has crossed out the possibility of reaching any sort of beneficial deal with Petro,” Rouvinski said.

Medina and Ante are the first foreign combatants of the war in Ukraine known to face service-related charges after being detained in a third country.

Both Russia and Ukraine have relied on thousands of foreigners to boost their depleted forces.

Some joined the war because they sought adventure, wanted to defend an ideological cause or because they hated the enemy. But many others — particularly from poorer countries in Latin America, Asia and Africa — went to Ukraine primarily to earn a living for their families.

Colombian fighters have proved particularly useful recruits for the Ukrainian military because of their experience fighting Marxist guerrillas and training with U.S. weapons and officers.

Hundreds of retired Colombian soldiers have traveled to Ukraine since the start of the war to fight for Kyiv for about $3,000 a month, more than they could make at home based on their skills, about a dozen Colombian recruits and their relatives said in interviews.

Ante and Medina had served in the Carpathian Sich 49th Infantry Battalion, one of the two main destinations for Latin American recruits in Ukraine’s armed forces.

Russia and Ukraine have sought to punish foreign nationals who joined the opposing side, to raise morale among their own citizens and deter others from joining the enemy.

Early in the war, a court in Russian-occupied Ukraine issued death sentences against two British nationals and a Moroccan who were taken prisoner while fighting for Ukraine. The sentences were never carried out, and the men were later repatriated in a prisoner exchange.

Since then, Russia has tried Ukraine’s foreign fighters mostly in absentia.

Ukraine has conducted similar trials against captured foreigners fighting for Russia. Most famously, a Ukrainian court convicted a Brazilian man on terrorism charges before eventually returning him to Brazil.

International law is ambiguous about the legality of foreigners such as Medina and Ante joining a faraway war, legal experts have said. Such men partly meet the definition of mercenaries, who are banned under the Geneva Conventions because they are motivated primarily by money and have no ties to combatant nations.

But because foreign fighters in Ukraine are members of the regular armed forces and receive similar payments and benefits as Ukrainian citizens, the Ukrainian government has claimed that they are legal combatants.

In addition to the Geneva Conventions, Russian law explicitly bans mercenaries. The Kremlin, however, has relied significantly on private military companies to recover from the setbacks of its invasion two years ago, and since last year has recruited heavily from nations such as Cuba, Nepal and Syria.