UN Secretary-General Ban Ki-moon strongly condemned the "appalling" attacks on Friday in France, Kuwait and Tunisia and said those responsible should face justice.
One person was decapitated in southeastern France while in Tunisia gunmen killed at least 28 people at a beach resort, while 25 people died in a suicide bombing claimed by Islamic State jihadists in Kuwait.
Ban condemned "in the strongest terms the terrorist attacks in Tunisia, Kuwait and France today," said a statement from his spokesman.
"Those responsible for these appalling acts of violence must be swiftly brought to justice."
Ban vowed that the "heinous attacks" will not weaken international resolve to fight terror but rather strengthen the commitment to defeat "those bent on murder, destruction and the annihilation of human development and culture."