India, April 20 -- As Israel launched a missile strike on Iran Friday, Tehran claimed to have activated its air defence system and that it shot down several drones.

Israel launched a strike against Iran in retaliation for its weekend attack, said US officials, though media from both countries appeared to downplay the severity of the incident.

Iran activated its air defence system over several cities, state media reported, soon after the countrys official broadcaster said explosions were heard near Isfahan, Irans third-biggest city.

Several Iranian nuclear sites are located in Isfahan province, including Natanz, the centerpiece of Irans uranium enrichment program.

Nuclear facilities in Isfahan were reported to be completely secure, Ira...