"During the fighting, eight professional soldiers were captured and on May 9 we received proof of life," Venezuelan Defense Minister Vladimir Padrino Lopez said in a televised statement.

"We denounce before the international community... the appalling kidnapping of these soldiers," he said.

Venezuela's armed forces have engaged in clashes with Colombian armed groups along the border since March 21, displacing thousands of civilians who fled to Colombia.

Venezuela does not name the armed groups it blames for the unrest, apart from calling them "terrorists" or linking them to drug trafficking or to Colombian President Ivan Duque.

However, security sources in Colombia say they are likely dissidents of the now-disbanded Revolutionary Armed Forces of Colombia (FARC) rebel group, an analysis Venezuelan President Nicolas Maduro has conceded was possible.

"We will spare no effort and we will exhaust all possible ways to recover them safe and sound," Padrino said of the soldiers, surrounded by members of the country's military brass.

Last Monday, Fundaredes, an NGO that is critical of Maduro, published documents from alleged FARC dissidents detailing how the eight soldiers were "captured as prisoners of war," in clashes with Venezuela.

In the documents, the dissidents appealed to the Red Cross to act as an intermediary for handing over the captives.

The Red Cross told AFP it was aware of the text, but would not comment on it at present.

According to Padrino, Venezuela's Ministry of Foreign Affairs is coordinating with the Red Cross to "serve as a link in the delivery" of the soldiers.

"We have established the necessary contacts for an early release," he said.

A total of 16 members of the Venezuelan armed forces have died since the clashes began, according to an official report by the Venezuelan Ministry of Defense.

Venezuela and Colombia, which share a 2,200-kilometer (1,370-mile) border, severed ties in January 2019, after Duque's government recognized opposition leader Juan Guaido as the leader of Venezuela over Maduro.