CARACAS — Opposition leader Juan Guaido, recognised by some 50 countries as Venezuela’s interim president, warned the military Sunday that blocking humanitarian aid from entering the country is a "crime against humanity."

The warning comes as international aid has taken center stage in a test of wills between Guaido and President Nicolas Maduro in which Venezuela’s armed forces are seen as the pivotal player.

Medicine and food sent by the United States has been blocked for three days on the border in Cucuta, Colombia after Venezuelan soldiers closed a bridge linking the two countries.

On the Venezuelan side of the border, dozens of doctors protested Sunday demanding the aid be allowed in -- including surgeon Jose Luis Mateus de la Riva, who accused Maduro of sinking Venezuelan medicine back to the "medieval era."

Maduro has rejected humanitarian aid as a US ploy to intervene in Venezuela, calling the deployment of aid a "political show" and blaming US sanctions for the country’s widespread shortages of food and medicine.

An international Contact Group, made up of European and Latin American countries, called for snap presidential elections following a meeting in Montevideo this week.

But Maduro, who has asked Pope Francis to act as a mediator, rejected what he said was "bias" by the group.

Last week Maduro also rejected a call by European Union countries to hold elections, prompting them to recognize Guaido. — AFP