Colombia will tighten control of over its porous border with Venezuela as thousands of migrants fleeing a rapidly deteriorating political and economic crisis escape into the neighboring Andean nation.

In a visit to a border city at the epicenter of Colombia's mounting migration crisis, President Juan Manuel Santos on Thursday announced new measures that could make it more difficult for Venezuelan migrants to cross into the country illegally or remain there without any official status.

"Colombia has never lived a situation like the one we are encountering today," Santos said.

Migration into Colombia has surged as Venezuelan President Nicolas Maduro has moved to consolidate his rule and the nation's economy plummets. Colombia migration authorities say there are an estimated 600,000 Venezuelans currently in Colombia — double the number six months ago. Venezuela exile associations and some border city officials have said they believe that number is higher.

The unprecedented migration wave is putting strains on Colombia at a delicate time in its history. The nation is crawling out of a five-decade-long armed conflict following the signing of a peace deal with leftist rebels in 2016. Many of the Venezuelans are arriving illegally and in need of medical attention.

"This is a tragedy," Santos said. "And I want to reiterate to President Maduro: This is the result of your policies."

More than 2,000 additional military officers will be deployed to control the hundreds of dirt-road crossings known as "trochas" that dot Colombia's 1,370-mile (2,200-kilometer) border with Venezuela. A new migration patrol unit will also police public spaces where Venezuelan arrivals congregate, provide them orientation and to control ills like prostitution that have surfaced in the migration wave's wake.

Migration authorities will no longer issue temporary border crossing cards, which have already been granted to 1.5 million Venezuelans to allow them short visits to purchase food and medicine. All Venezuelans inside the country will also be required to present themselves to officials and enroll in a registry.

Santos said Colombia wants to extend its solidarity to needy Venezuelans and will open a migrant center capable of providing aid to an estimated 2,000 people in the near future. But he also stressed that migration from Venezuela to Colombia needs to be conducted in a safe and legal manner.