A foreign affairs journalist says Iran will have to respond to the assassination of a Hamas' leader.  

Iran's vowing to avenge the killing of Ismail Haniyeh after his reported death in an air strike in Tehran. 

Hamas and Iran are blaming Israel, which has so far made no comment.  

It follows an Israeli strike in Lebanon, that killed a top Hezbollah commander.  

The Spectator foreign affairs columnist Paul Wood told Mike Hosking the Iranian Supreme Leader has made it known through various officials' comments that there will be a response.  

He says from their point of view, they have to restore their credibility in their allies' eyes, as this is a humiliation for them. 

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