The Iranian Revolutionary Guards said on Friday that its navy has new cruise missiles equipped with highly explosive warheads that are undetectable, state media reported.

The announcement by the country’s most powerful security organization coincides with fears of a full-blown Middle East war after Iran vowed to avenge the assassination in Tehran on July 31 of Ismail Haniyeh, leader of the Palestinian Islamist Hamas.

Iran has blamed Israel, while Israel has neither confirmed nor denied involvement.

“In today’s world you either have to be powerful to survive, or surrender. There’s no middle ground,” said the Guards’ top commander, Major-General Hossein Salami.