There are fears of a possible major escalation in the conflict in the Middle East.
Hezbollah is blaming Israel for an attack in Beirut, the capital of Lebanon, where the group has its political and military power base.
It says the explosion - which killed a top Hamas official - will never pass without response or punishment.
But Florencia Soto Nino, who's a spokesperson for the Secretary-General of the United Nations, is urging calm:
"We are calling for maximum restraints from all parties. We don't want any rash actions that could trigger further violence".
