The United States on Friday accused Russia of violating nuclear safety principles in Ukraine and demanded its invading forces stop firing on nuclear power plants, but added that there were no signs detected yet of any radiological release.

US Energy Secretary Jennifer Granholm said in a Twitter post that radiation monitors in much of Ukraine were still functioning although the United States was concerned by lack of data from safeguards monitors at Chernobyl or Zaporizhzhia, which is Europe's largest nuclear power...