Israel's military announced that it was carrying out a "series of strikes" around the Iranian capital Tehran and other areas of Iran.
The intended targets of the strikes were not immediately disclosed. The strikes came after Israel said it had intercepted a "suspicious aerial target" launched from Iran.
Earlier, the Iranian semi-official news agency SNN reported that air defense systems had been activated in central Tehran.
The Israeli Defence Forces (IDF) also advised Iranians in two villages to evacuate the area around Iran's Arak heavy water reactor.
Heavy water is used to cool reactors but can also be used to produce plutonium, another possible source for a nuclear weapon.
"The IDF issues an urgent warning to residents, workers and those present in the area of the two Iranian cities of Arak and Khondab, in the areas marked on the map, to evacuate immediately before the IDF targets military infrastructure belonging to the Iranian regime," it wrote on social media in Arabic and Farsi.
German, French, British foreign ministers to meet Iranian counterpart
The foreign ministers of Germany, France and the United Kingdom are set to meet with their Iranian counterpart in Geneva, Switzerland, on Friday, news agencies reported on Wednesday evening, citing diplomatic sources.
The meeting is being coordinated by German Foreign Minister Johann Wadephul, who who recently changed plans to visit Lebanon, Syria and Israel to instead hold crisis talks in Saudi Arabia, Qatar and Oman following Israel's strikes on Iran last Friday.
Muscat, in particular, is believed to maintain very strong contacts with Tehran and had been mediating in negotiations between the United States and Iran for nearly two months prior to Israel's attack.
The meeting was reportedly being coordinated with Washington.
Wadephul is hoping to launch an initiative involving the so-called "E3" — Germany, France and the UK — as well as with neighboring Arab states such as Oman to help bring about a diplomatic solution to the current conflict.
"It's never too late to come to the negotiating table," Wadephul said earlier in the day.