Costa Rica filed a complaint against neighboring Nicaragua to the International Court of Justice (ICJ), the UN's highest court, on Monday, claiming Nicaragua set up a military post on its territory in 2016.

Costa Rica said following a December 2015 ICJ ruling that gave Costa Rica sovereignty over a small area of wetlands near the San Juan River, called Isla Portillos by Costa Rica and Harbor Head by Nicaragua, that Nicaragua had set up a new military camp in the area.

"[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," said Costa Rican Foreign Minister Manuel Gonzalez in a statement. Gonzalez expects a ruling by the ICJ by the beginning of 2018.

The government of Nicaragua did not immediately comment on the matter.

Rocky waters

Costa Rica and Nicaragua have had intense border disputes in recent years centering on the San Juan River. In 2010, Costa Rica first complained to the ICJ that Nicaragua's army occupied a three-square-kilometer (1.86-square-mile) area near the mouth of the San Juan River as it flows into the Caribbean Sea.

In a 2011 counter-claim, Nicaragua argued to the ICJ that Costa Rica was causing damage to the environment by building a road next to the river.

The December 2015 ruling by the ICJ found Nicaragua violated Costa Rican sovereignty over the area, and Nicaragua had one year to reach an agreement on compensation to Costa Rica, but Costa Rica's northern neighbor did not respond to its $6.7 million (6.3 million euro) compensation estimate.

The border between Costa Rica and Nicaragua was established with the Canas-Jerez Treaty in 1858, which states the San Juan River belonged to Nicaragua, but Costa Rica was given commercial access to the river. The treaty has since been reinterpreted many times.

kbd/gsw (AFP, Reuters)