Israel's prime minister has launched a stinging attack on Iran, telling a security conference in Munich it is the "greatest threat to our world".
Benjamin Netanyahu said Israel would "not allow Iran's regime to put a noose of terror around our neck".
In a moment of drama, he brandished what he said was a piece of an Iranian drone shot down in Israeli territory.
Iran's foreign minister later dismissed the speech as "cartoonish" and not worthy of a response.
BBC diplomatic correspondent Jonathan Marcus, at the conference, says this theatricality was vintage Benjamin Netanyahu, from a prime minister embattled at home with potential corruption charges looming over his head.
The former US Secretary of State John Kerry later insisted that Mr Netanyahu's assertion that Iran would be on its way to a nuclear bomb within a decade was "fundamentally not accurate".
In his speech, Mr Netanyahu drew a parallel between the 1938 Munich Agreement, seen as a failed attempt to appease Nazi Germany, and the 2015 Iran nuclear deal.
He said the deal had only "unleashed a dangerous Iranian tiger", against which "we will act without hesitation to defend ourselves".
Holding up the remnant of drone, of which Iran denies ownership, he addressed Mr Zarif directly: "Do you recognise this? You should, it's yours. You can take back a message to the tyrants of Tehran: Do not test Israel's resolve."
How did Iran respond?
Speaking later, Mr Zarif called for a new security arrangement for the nations of the Gulf region, warning that without this there would be turmoil.
He insisted that Iran was "not devouring the entire region - we don't believe that's in our interest or even possible. So we need to start talking instead".
He deflected a question about whether Iran could recognise Israel, accusing Israel of using "aggression as a policy against its neighbours" and the Palestinians, and saying it was "trying to escape responsibility for its criminal policies".
As for the nuclear deal, he insisted "we will not be the first ones to violate an agreement which we did everything to achieve - despite Mr Netanyahu's efforts".
Why the recent spike in tensions?
The immediate trigger is last week's confrontation - the first known direct engagement between the Israeli and Iranian militaries.
Israel launched raids against Iranian targets in Syria after saying it had intercepted an Iranian drone crossing the Syria-Israel border.
During the offensive, an Israeli F-16 fighter jet was shot down by Syrian air defences, its pilots ejecting in northern Israel.
It was believed to be the first time Israel had lost a jet in combat since 2006.
What about in the longer term?
The rivalry between Iran and Israel has been exacerbated in recent years by the regional instability - from the toppling of Saddam Hussein's regime in Iraq, which removed a counterweight to Iranian regional power, to the ongoing proxy war being fought between many different powers in Syria.
Israel is a vocal opponent of the 2015 deal struck between Iran and six world powers which lifted sanctions in exchange for curbs on Iran's nuclear programme.
It is a debatable point whether Mr Netanyahu or Mr Zarif was the most welcome guest in Munich, says the BBC's Jonathan Marcus.
While there is strong support in Europe for the nuclear deal with Iran, there is a growing sense in several capitals that more must be done to curb Iran's destabilising regional role.
It has emerged as one of the great victors from the chaos in Syria.
How will the speech be seen from Israel?
The Israeli prime minister was speaking with the huge shadow of potential corruption charges hanging over his head.
He is likely to have directed his Munich appearance as much at his domestic audience as to the wider international community, our correspondent says, insisting that he remains the essential leader for Israel at a time of growing regional competition.