VIENNA, July 5 - Experts from the U.N. nuclear watchdog based at the Russian-held Zaporizhzhia nuclear power plant in Ukraine have yet to observe any indications of mines or explosives at the plant, but they need more access to be sure, the agency said on Wednesday.

Russia and Ukraine on Tuesday accused each other of plotting to stage an attack on Europe's biggest nuclear power plant, where the International Atomic Energy Agency has repeatedly warned of potential catastrophe from nearby military clashes.