Colombia is demanding an explanation from Venezuela after spotting two military aircraft flying in Colombian airspace, the defense ministry said Sunday. The confrontation comes amid a larger diplomatic rupture between the countries as Venezuelan President Nicolas Maduro has closed major border crossings and deported of thousands of Colombian nationals.

Colombia’s aerial defense systems detected two Venezuelan military planes entering its airspace over the northern La Guajira province Saturday afternoon, the defense ministry said in a statement, according to news agency Efe. The ministry said it transmitted information about the airspace violation to the foreign ministry’s office “so that it will ask Venezuela for relevant explanations for these acts.”

The statement came just a day after both countries’ foreign ministers met in Ecuador’s capital of Quito to try to forge an agreement over the simmering border dispute that began when Maduro closed off a section of the border last month. The ministers agreed to renew diplomatic ties that had been cut off when the dispute began, but were unable to set up a meeting between Maduro and Colombia’s President Juan Manuel Santos to resolve the crisis.

Maduro closed off two major border crossings with Colombia Aug. 20, saying that Colombian paramilitary groups were behind the attack of three Venezuelan soldiers and a civilian who were attacked near the border the day before. Since then, Venezuelan officials have deported around 1,300 undocumented immigrants from Colombia living near the border, and reports of families being separated or people being deported without their belongings have proliferated. An additional 21,000 Colombians living in Venezuela have also fled the country for fear of being forcibly removed, according to the U.N. Office for Humanitarian Affairs.

Border activity had been a source of tension between the countries for years, as Maduro blamed smugglers for taking goods out of Venezuela to fetch higher prices next door. Santos has blasted the deportations, saying they were not carried out humanely. A recent survey by Venezuelan polling firm Hinterlaces published Sunday, however, found that 61 percent of Venezuelans supported the border closures.

Many analysts have viewed the crisis as a way for Maduro to distract the populace from Venezuela’s own economic and political turmoil. Santos hinted at that in a speech earlier this week: “The closing of the border is not the fault of Colombia, and every day it is clearer that it is due to other interests,” he said.