ZAGREB, Croatia: Croatia's doctors on Thursday (Friday in Manila) warned the public against consuming iodine as demand surged for the substance over fears that Russia may use nuclear weapons during its ongoing invasion of Ukraine. Residents across Croatia have been panic buying iodine since Russian President Vladimir Putin ordered his country's nuclear forces to be put on high alert. 'The (iodine tablets) can cause serious side effects,' read a statement released by the Croatian Medical Chamber, adding that the pills can affect thyroid gland functions and cause allergic reactions. According to the World Health Organization protocols, potassium iodide tablets are recommended for certain groups — including children, pregnant women and people under 40 years of age — to prevent the development of thyroid cancer after a nuclear attack, the statement added. Moscow has the world's largest arsenal of nuclear weapons and a huge cache of ballistic missiles, which form the backbone of its deterrent forces.