Thousands of Venezuelans have broken through barricades along the international border with Colombia, according to the migration office in Bogota, which warned Venezuelan President Nicolas Maduro he would be held responsible for any problems that may occur.
Maduro in February blocked bridges joining the two nations in a bid to prevent a US-backed effort to distribute humanitarian aid to the crisis-wracked nation.
With bridges blocked by containers and trucks, Venezuelans have been wading through the Tachira River to reach the city of Cucuta, on Colombia's northern border, to find food, medicines and work.
But torrential rain in recent days has made that impossible.
"The usurper Maduro is responsible for anything that may happen to the population that is transiting between the two countries," Christian Kruger, head of Colombia's migration agency, said.
Millions of Venezuelans have fled to Colombia to escape widespread shortages of food and medicine in their homeland, seeking jobs locally and passage into other Latin American countries.
Venezuela plunged into a deep political crisis in January when Juan Guaido, head of the opposition-controlled congress, invoked the constitution to assume an interim presidency, arguing Maduro's 2018 re-election was not legitimate.
US President Donald Trump has taken steps to ratchet up pressure on Maduro and bolster Guaido, who has been recognised as president by the US and more than 50 other countries, including Colombia.
