Costa Rica’s government said on Monday it has filed a complaint against Nicaragua at the International Court of Justice for establishing a military post on its territory, heightening the risk of renewed tensions between the two nations.

Costa Rican foreign minister Manuel Gonzalez said Nicaragua had occupied a beach on Isla Calero in northeastern Costa Rica in November 2016, a virtually uninhabited area where both countries have a historic border dispute.

“(Nicaragua) has installed a military post in a small strip of that Costa Rican territory. We took diplomatic steps … so that they would remove it, which did not happen,” Gonzalez said in a statement.