Iran has arrested dozens of people on suspicion of spying as fears grow in the Islamic Republic over the extent of its infiltration by Israel’s Mossad intelligence service.

Oman and Qatar were leading efforts to begin ceasefire talks, while mediators said Iran was open to resuming nuclear negotiations if Israel’s attacks stop.

Iran's strikes on Israel are self-defense and are "proportionate defensive operations directed exclusively at military objectives and associated infrastructure," Iran's U.N. Ambassador Amir Saeid Iravani told the U.

Blasts rang out across a swath of the Middle Eastern republic’s territory, targeting its nuclear capabilities, military leadership and scientists.

Since Israel began its concerted attack on Iran on Friday, calls for regime change in Iran have grown louder – from hawks in the US Congress to Israeli officials and some Iranian activists abroad.

Israel's airstrikes have deepened a climate of fear within Iran, where there is a shortage of reliable information. A woman in Tehran said one of the worst things about the attacks is that they usually come without warning.

As the attacks escalate, with fatalities and injuries reported on both sides, Israel issued the stark warning to Iran.