The foreign ministry dispatched a note of protest Tuesday to Harold Rivas, the Nicaraguan ambassador here.
The note energetically protested the violation of terms that the International Court of Justice set down March 8, 2011, the Ministerio de Relaciones Exteriores y Culto said.
The fence and barbed wire is along a narrow canal that Nicaraguan troops dug more than two years ago. Photos released by the foreign ministry here are unimpressive. They show a few posts and sagging wire. One photo shows a pole with a Nicaraguan flag at the top, but that could have been erected some time ago. There appears to be just one strand of wire on the posts.
The area on the Isla Calero and Isla Portillos had been occupied by Nicaraguan troops, but they left before the issue went to the World Court. Periodically young Sandinista activists invade the area and spend a few days there.
Costa Rica blamed the fence on Nicaraguans.
As with past protests, Nicaraguan officials are likely to ignore this one.
Under terms of the temporary court ruling, Costa Rica has the right to enter the area and conduct efforts to protect the environment. Nicaraguans are not supposed to be there.