Costa Rican Foreign Minister Enrique Castillo has expressed concerns that Nicaragua is "entering into a relationship of military dependency with Russia."
In an interview published on May 4 in the "La Nacion" daily, Castillo said "Russia is facilitating the arming of Nicaragua -- ships -- and they have spoken about buying jets and other weapons.”
Costa Rica and Nicaragua have border disputes before the International Court of Justice.
Last month, Nicaraguan President Daniel Ortega said his country was "committed to further strengthening and modernizing the army" with the help of any country willing to provide aid.
Russia's ambassador to Managua confirmed in March that Moscow wants to build a military resupply base in Nicaragua.
Russian Defense Minister Sergei Shoigu has said Russia is considering whether to increase its military presence in Nicaragua, Cuba, and Venezuela.
Russian Foreign Minister Sergei Lavrov visited Nicaragua last week.
Based on reporting by AFP and "La Nacion"